Multipoint fixation implants and related methods

ABSTRACT

Bone anchor assemblies are disclosed herein that can provide for improved fixation as compared with traditional bone anchor assemblies. An exemplary assembly can include a bracket or wing that extends down from the receiver member. The distal portion of the wing can define a bone anchor opening through which one or more auxiliary bone anchors can be disposed to augment the fixation of the assembly&#39;s primary bone anchor. A distal surface of the distal portion of the wing can be obliquely angled relative to a proximal-distal axis of the spanning portion to face one of a caudal direction or a cephalad direction. A distal surface of the distal portion of the wing can be obliquely angled relative to the proximal-distal axis of the spanning portion to face one of a medial direction or a lateral direction. Surgical methods using the bone anchor assemblies described herein are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/124,152, filed Dec. 16, 2020. U.S. application Ser. No. 17/124,152 isa continuation of U.S. application Ser. No. 15/926,069, filed Mar. 20,2018, now issued as U.S. Pat. No. 10,898,232. The entire contents ofeach of these applications is incorporated herein by reference.

FIELD

Orthopedic implants and related methods are disclosed herein. Forexample, bone anchor assemblies with multiple bone engagement points aredisclosed.

BACKGROUND

Bone anchor assemblies can be used in orthopedic surgery to fix boneduring healing, fusion, or other processes. In spinal surgery, forexample, bone anchor assemblies can be used to secure a spinal fixationelement to one or more vertebrae to rigidly or dynamically stabilize thespine. Bone anchor assemblies can also be used as an engagement pointfor manipulating bone (e.g., distracting, compressing, or rotating onevertebra with respect to another vertebra, reducing fractures in a longbone, and so forth).

The integrity with which the bone anchor assembly engages the bone canaffect the transfer of corrective biomechanical forces. While a greatamount of care is exercised when placing bone anchor assemblies, it iscommon that a bone anchor assembly will be inserted in a compromisedstate. For example, the bone opening in which the assembly is disposedcan be stripped (e.g., by driving the bone anchor assembly past itsoptimum holding position), the bone anchor assembly can be placedincorrectly (e.g., using an incorrect instrument maneuver such as anover-sized pilot hole), the bone anchor assembly can be placed outsideof its intended trajectory (e.g., within a facet capsule or breachedthrough a pedicle wall), or the bone anchor assembly can be insertedinto compromised bone (e.g., bone that is fractured, osteoporotic,diseased, or otherwise lacking in structural integrity).

When the bone anchor assembly is in a compromised state, there can besub-optimal purchase between the bone anchor assembly and the bone. Thebone anchor assembly may feel unsecure to the surgeon, and it ispossible that the bone anchor assembly could back out or become loosenedover time. There are limited options for the surgeon when faced withthese types of situations. In spinal surgery, for example, the surgeoncan remove the bone anchor assembly and skip the vertebral level, thoughthis can undesirably require expanding the surgical site to additionalvertebral levels. The surgeon can remove and re-insert with a largeranchor, though this may not be an option when space for anchoring in thebone is limited. The surgeon can leave the compromised bone anchorassembly in place, which may be the safest alternative if the boneanchor assembly is in a safe location and attachment to the plate, rod,or other implant construct is definitive, as the additional compromisedfixation may be better than removal.

Even when a bone anchor assembly is placed in a non-compromised state,the geometry of traditional bone anchor assemblies can limit theflexibility with which the bone attachment point can be located withrespect to a plate, rod, or other implant construct coupled to the boneanchor assembly.

There is a continual need for improved bone anchor assemblies andrelated methods.

SUMMARY

Bone anchor assemblies are disclosed herein that can provide forimproved fixation as compared with traditional bone anchor assemblies.An exemplary assembly can include a bracket or wing that extends downfrom the receiver member and accommodates one or more auxiliary boneanchors that augment the fixation of the assembly's primary bone anchor.Another exemplary assembly can include a plate that is seated betweenthe receiver member and the rod and accommodates one or more auxiliarybone anchors that augment the fixation of the assembly's primary boneanchor. Another exemplary assembly can include a hook that extends outfrom the receiver member to hook onto an anatomical structure or anotherimplant to augment the fixation of the assembly's primary bone anchor.Surgical methods using the bone anchor assemblies described herein arealso disclosed.

In some embodiments, a bone anchor assembly includes a bone anchor; areceiver member coupled to a proximal end of the bone anchor anddefining a recess configured to receive a rod; a closure mechanismthreadably mated to the receiver member; a wing having a proximalportion disposed proximal to the receiver member, a distal portion thatdefines a bone anchor opening, and a spanning portion that connects theproximal and distal portions; and a nut configured to threadably engagethe closure mechanism to secure the proximal portion of the wing to theproximal end of the receiver member.

The closure mechanism can be or can include a threaded post. The wingcan include an opening through which at least a portion of the threadedpost is disposed. The wing can be rotatable about the closure mechanism.A distal-facing surface of the proximal portion of the wing can bearagainst a proximal terminal end of the receiver member. A lateralsurface of the distal portion of the wing can form a negative of asidewall of the receiver member. A lateral surface of the spanningportion of the wing can form a negative of a sidewall of the receivermember. A lateral surface of the spanning portion of the wing caninclude a protrusion that engages a corresponding recess formed in thereceiver member. The spanning portion can hug the sidewall of thereceiver member. The receiver member can be polyaxially movable relativeto the bone anchor. The assembly can include an auxiliary bone anchordisposed in the bone anchor opening of the distal portion of the wing.The proximal-most extent of the auxiliary bone anchor can be distal to arod when the rod is disposed in the recess of the receiver member. Theproximal-most extent of the auxiliary bone anchor can be distal to thedistal-most extent of the receiver member. The spanning portion can havean adjustable height. The spanning portion can include first and secondlegs movable toward one another to increase the height of the spanningportion and movable away from one another to decrease the height of thespanning portion. The spanning portion can be deformable to allow thedistal portion of the wing to be angled to match an abutting bonesurface.

In some embodiments, a method of securing a bone anchor assembly to boneincludes driving a bone anchor into bone, the bone anchor having areceiver member coupled to a proximal end thereof; positioning a rod inthe receiver member; attaching a closure mechanism to the receivermember to retain the rod in the receiver member; coupling a proximalportion of a wing to at least one of the closure mechanism and aproximal surface of the receiver member; and inserting an auxiliary boneanchor through a bone anchor opening formed in a distal portion of thewing and driving the auxiliary bone anchor into the bone.

Coupling the proximal portion of the wing can include inserting at leasta portion of the closure mechanism through an opening formed in theproximal portion of the wing. The method can include rotating the wingrelative to receiver member to position the bone anchor opening of thewing with respect to a target location on the bone. The method caninclude deforming the wing to position the bone anchor opening of thewing with respect to a target location on the bone. The method caninclude adjusting a height of the wing such that the wing spans from theproximal-most extent of the receiver member to the bone. The bone anchorand the auxiliary bone anchor can be driven into a single vertebra.

In some embodiments, a bone anchor assembly includes a bone anchor; areceiver member coupled to a proximal end of the bone anchor anddefining a recess configured to receive a rod; a closure mechanismthreadably mated to the receiver member; a plate having a primaryopening through which first and second arms of the receiver memberextend, a bone anchor opening, and a saddle portion that extends acrossat least a portion of the primary opening such that the saddle portionis disposed in the recess of the receiver member; and an auxiliary boneanchor disposed through the bone anchor opening of the plate.

The assembly can include a rod disposed between the saddle portion ofthe plate and the closure mechanism. The saddle portion can be movablycoupled to the plate. A distal facing surface of the saddle portion canform a section of a cylinder. The primary opening in the plate can bedefined by a first sidewall. The bone anchor opening of the plate can bedefined by a second sidewall. A height of the first sidewall can bereduced where the first sidewall meets the second sidewall. The assemblycan include a cap configured to engage the first and second arms of thereceiver member. The cap can define a central opening disposed proximalto a proximal-most extent of the receiver member. The central openingcan receive at least a portion of the closure mechanism therethrough.The proximal-most extent of the auxiliary bone anchor can be distal to arod when the rod is disposed in the recess of the receiver member. Theproximal-most extent of the auxiliary bone anchor can be distal to thedistal-most extent of the receiver member.

In some embodiments, a method of securing a bone anchor assembly to boneincludes driving a bone anchor into bone, the bone anchor having areceiver member coupled to a proximal end thereof; inserting first andsecond arms of the receiver member through a primary opening of a platesuch that a saddle portion of the plate is disposed in a rod-receivingrecess of the receiver member; positioning a rod on a proximal-facingsurface of the saddle portion such that the rod is disposed in therod-receiving recess of the receiver member; attaching a closuremechanism to the receiver member to retain the rod in the receivermember; and inserting an auxiliary bone anchor through a bone anchoropening formed in the plate and driving the auxiliary bone anchor intothe bone.

The method can include bending the plate to position the bone anchoropening against the bone. The method can include bending the saddleportion of the plate to position the bone anchor opening against thebone. The bone anchor and the auxiliary bone anchor can be driven into asingle vertebra.

In some embodiments, a bone anchor assembly includes a bone anchor; areceiver member coupled to a proximal end of the bone anchor anddefining a recess configured to receive a rod; a closure mechanismthreadably mated to the receiver member; a plate having a primaryopening through which at least a portion of the receiver member extends,a bone anchor opening, and a distal-facing portion that extends across aproximal-facing portion of the receiver member; and an auxiliary boneanchor disposed through the bone anchor opening of the plate.

In some embodiments, a bone anchor assembly includes a bone anchor; areceiver member coupled to a proximal end of the bone anchor anddefining a recess configured to receive a rod; a closure mechanismthreadably mated to the receiver member; and a hook having a bodyportion coupled to the receiver member and a curved extension projectingfrom the body portion.

The extension can be substantially U-shaped. The extension can define aninside curved surface and an outside curved surface. The inside curvedsurface can form a substantial negative of a lamina. The body portioncan have a lateral sidewall that abuts a sidewall of the receivermember. The hook can be coupled to the receiver member by a collar. Thecollar can define a first opening in which the receiver member isdisposed and a second opening through which a locking screw is disposed.The locking screw can threadably engage the body portion of the hook.The first opening can include an engagement feature that engages acorresponding engagement feature formed in or on an exterior of thereceiver member. The second opening can have a tapered shape to pull thereceiver member towards the body portion as the locking screw istightened. The collar can be disposed proximal to a rod when the rod isdisposed in the receiver member. The collar can extend around an outerperiphery of the receiver member. The hook can be configured to pivotwith the receiver member relative to the bone anchor. The hook can becoupled to the receiver member by a nut. The nut can be threaded ontothe closure mechanism to compress a proximal portion of the hook againsta proximal end of the receiver member.

In some embodiments, a method of securing a bone anchor assembly to boneincludes driving a bone anchor into bone, the bone anchor having areceiver member coupled to a proximal end thereof; positioning a rodwithin a rod-receiving recess of the receiver member; attaching a hookto the receiver member and hooking an extension of the hook onto atleast one of an anatomical structure and an implant; and attaching aclosure mechanism to the receiver member to retain the rod in thereceiver member.

The bone anchor can be driven into a first vertebra and the extension ofthe hook can be hooked onto a lamina of the first vertebra. The hook canbe attached to the receiver member after the bone anchor is driven intothe bone. The closure mechanism can be attached to the receiver memberafter the hook is attached to the receiver member. The hook can beattached to the receiver member after the rod is seated in the receivermember.

In some embodiments, a bone anchor assembly can include a bone anchor;an auxiliary bone anchor; a receiver member coupled to a proximal end ofthe bone anchor and defining a rod seat configured to receive a rod; aclosure mechanism threadably mated to the receiver member; a wing thatincludes a proximal portion, a distal portion, and a spanning portionthat connects the proximal and distal portions, the proximal portionhaving a distal-facing surface that opposes a proximal terminal end ofthe receiver member and defines an opening through which at least aportion of the closure mechanism is disposed, the spanning portionextending vertically along a side wall of the receiver member betweenthe proximal portion and the distal portion, the distal portionextending outward from a distal end of the spanning portion; and a nutconfigured to threadably engage the closure mechanism to secure theproximal portion of the wing to the receiver member. The distal portionof the wing can define a bone anchor opening through which the auxiliarybone anchor can be disposed. The distal surface of the distal portion ofthe wing can be obliquely angled relative to a proximal-distal axis ofthe spanning portion to face one of a caudal direction or a cephaladdirection.

The distal surface of the distal portion of the wing can be obliquelyangled to the right of the proximal-distal axis of the spanning portion.The distal surface of the distal portion of the wing can be obliquelyangled to the left of the proximal-distal axis of the spanning portion.The distal surface of the distal portion of the wing can be obliquelyangled relative to a proximal-distal axis of the spanning portion suchthat a central axis of the bone anchor opening extends in one of acaudal direction or a cephalad direction and in one of a medialdirection or a lateral direction when the wing is secured to thereceiver member.

The distal surface of the distal portion of the wing can be obliquelyangled inward and to the right of the proximal-distal axis of thespanning portion. The distal surface of the distal portion of the wingcan be obliquely angled outward and to the right of the proximal-distalaxis of the spanning portion. The distal surface of the distal portionof the wing can be obliquely angled inward and to the left of theproximal-distal axis of the spanning portion. The distal surface of thedistal portion of the wing can be obliquely angled outward and to theleft of the proximal-distal axis of the spanning portion. A proximalsurface of the distal portion of the wing can be substantially parallelto the distal surface of the distal portion.

In some embodiments, a bone anchor assembly can include a bone anchor;an auxiliary bone anchor; a receiver member coupled to a proximal end ofthe bone anchor and defining a rod seat configured to receive a rod; aclosure mechanism threadably mated to the receiver member; a wing thatincludes a proximal portion, a distal portion, and a spanning portionthat connects the proximal and distal portions, the proximal portionhaving a distal-facing surface that opposes a proximal terminal end ofthe receiver member and defines an opening through which at least aportion of the closure mechanism is disposed, the spanning portionextending vertically along a side wall of the receiver member betweenthe proximal portion and the distal portion, the distal portionextending outward from a distal end of the spanning portion; and a nutconfigured to threadably engage the closure mechanism to secure theproximal portion of the wing to the receiver member. The distal portionof the wing can define a bone anchor opening through which the auxiliarybone anchor can be disposed. A distal surface of the distal portion ofthe wing can be obliquely angled relative to a proximal-distal axis ofthe spanning portion to face one of a medial direction or a lateraldirection.

The distal surface of the distal portion of the wing can be obliquelyangled inward towards the proximal-distal axis of the spanning portion.The distal surface of the distal portion of the wing can be obliquelyangled outward away from the proximal-distal axis of the spanningportion. A proximal surface of the distal portion of the wing can besubstantially parallel to the distal surface of the distal portion.

In any of the foregoing embodiments, the auxiliary bone anchor can havea threaded proximal head. The bone anchor opening can have a partiallythreaded interior surface configured to engage the threaded proximalhead of the auxiliary bone anchor such that the auxiliary bone anchorcan be capable of being locked at any angle amongst multiple selectableangles relative to the central axis of the bone anchor opening. Theclosure mechanism can include a threaded post having a radiallyextending shoulder portion. A counter bore can be formed about theopening in the distal-facing surface of the proximal portion of the wingto accommodate the radially extending shoulder portion extending atleast partially above the proximal terminal end of the receiver member.The bone anchor opening defined in the distal portion of the wing caninclude multiple bone anchor openings. A central axis of the bone anchoropening can be substantially perpendicular to the distal surface of thedistal portion such that the central axis of the bone anchor openingextends in the medial direction or the lateral direction. The wing caninclude a unilateral locking interface configured to enable a surgicalinstrument to hold onto one side of the wing.

In some embodiments, a method of securing a bone anchor assembly to bonecan include driving a bone anchor into bone, the bone anchor having areceiver member coupled to a proximal end thereof; positioning a rod ina rod seat defined in the receiver member; attaching a closure mechanismto the receiver member to retain the rod in the receiver member;coupling a proximal portion of a wing to at least one of the closuremechanism and a proximal terminal end of the receiver member, such thata spanning portion of the wing extends vertically along a side wall ofthe receiver member between the proximal portion and a distal portion ofthe wing that extends outward from a distal end of the spanning portion;and driving the auxiliary bone anchor through a bone anchor openingformed in the distal portion of the wing into bone at an oblique anglein one of a caudal direction or a cephalad direction. A distal surfaceof the distal portion of the wing can be obliquely angled relative to aproximal-distal axis of the spanning portion to face the caudaldirection or the cephalad direction.

Driving the auxiliary bone anchor through the bone anchor opening intobone can include driving the auxiliary bone anchor through the boneanchor opening at an oblique angle in a cephalad direction such that thebone anchor and the auxiliary bone anchor can be respectively driveninto a same vertebral level. Driving the auxiliary bone anchor throughthe bone anchor opening into bone can include driving the auxiliary boneanchor through the bone anchor opening at an oblique angle in a caudaldirection such that the bone anchor and the auxiliary bone anchor can berespectively driven into adjacent vertebral levels.

In some embodiments, a method of securing a bone anchor assembly to bonecan include driving a bone anchor into bone, the bone anchor having areceiver member coupled to a proximal end thereof; positioning a rod ina rod seat defined in the receiver member; attaching a closure mechanismto the receiver member to retain the rod in the receiver member;coupling a proximal portion of a wing to at least one of the closuremechanism and a proximal terminal end of the receiver member, such thata spanning portion of the wing extends vertically along a side wall ofthe receiver member between the proximal portion and a distal portion ofthe wing that extends outward from a distal end of the spanning portion;and driving the auxiliary bone anchor through a bone anchor openingformed in the distal portion of the wing into bone at an oblique anglein one of a medial direction or a lateral direction. A distal surface ofthe distal portion of the wing can be obliquely angled relative to aproximal-distal axis of the spanning portion to face the medialdirection or the lateral direction.

Driving the auxiliary bone anchor through the bone anchor opening intobone can include driving the auxiliary bone anchor through the boneanchor opening at an oblique angle in the medial direction such that thebone anchor and the auxiliary bone anchor can be respectively driveninto a same vertebral level. Driving the auxiliary bone anchor throughthe bone anchor opening into bone can include driving the auxiliary boneanchor through the bone anchor opening at an oblique angle in thelateral direction such that the bone anchor and the auxiliary boneanchor can be respectively driven into a same vertebral level.

In any of the foregoing embodiment methods, the closure mechanism caninclude a threaded post having a radially extending shoulder portion.Coupling the proximal portion of the wing to at least one of the closuremechanism and the proximal terminal end of the receiver member caninclude disposing at least a portion of the threaded post through theopening formed in the proximal portion of the wing; and receiving theradially extending shoulder portion that extends at least partiallyabove the proximal terminal end of the receiver member in a counter boreformed about the opening in the distal-facing surface of the proximalportion of the wing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an exploded perspective view of a prior art bone anchorassembly;

FIG. 1B is a sectional view of the bone anchor assembly of FIG. 1A;

FIG. 1C is a perspective view of the bone anchor assembly of FIG. 1Ashown with extension tabs;

FIG. 2A is a perspective view of a bone anchor assembly and a spinalrod;

FIG. 2B is a perspective exploded view of the bone anchor assembly andspinal rod of FIG. 2A;

FIG. 2C is a perspective view of the bone anchor assembly and spinal rodof FIG. 2A;

FIG. 2D is a top view of the bone anchor assembly and spinal rod of FIG.2A;

FIG. 2E is a perspective view of a wing of the bone anchor assembly ofFIG. 2A;

FIG. 2F is another perspective view of a wing of the bone anchorassembly of FIG. 2A;

FIG. 2G is another perspective view of a wing of the bone anchorassembly of FIG. 2A;

FIG. 2H is another perspective view of a wing of the bone anchorassembly of FIG. 2A;

FIG. 2I is a perspective view of the bone anchor assembly and spinal rodof FIG. 2A, shown with an adjustable-height wing;

FIG. 2J is a perspective view of a wing of the bone anchor assembly ofFIG. 2I;

FIG. 2K is another perspective view of a wing of the bone anchorassembly of FIG. 2I;

FIG. 2L is another perspective view of a wing of the bone anchorassembly of FIG. 2I;

FIG. 2M is another perspective view of a wing of the bone anchorassembly of FIG. 2I;

FIG. 3A is a perspective view of a bone anchor assembly and a spinalrod;

FIG. 3B is a perspective exploded view of the bone anchor assembly andspinal rod of FIG. 3A;

FIG. 3C is a perspective view of a plate of the bone anchor assembly ofFIG. 3A;

FIG. 3D is another perspective view of a plate of the bone anchorassembly of FIG. 3A;

FIG. 3E is another perspective view of a plate of the bone anchorassembly of FIG. 3A;

FIG. 3F is another perspective view of a plate of the bone anchorassembly of FIG. 3A;

FIG. 3G is a perspective view of a receiver member and plate of the boneanchor assembly of FIG. 3A;

FIG. 3H is a perspective view of the bone anchor assembly and spinal rodof FIG. 3A, shown with a cap;

FIG. 3I is a perspective view of a human spine with the bone anchorassembly and spinal rod of FIG. 3A coupled thereto;

FIG. 4A is a perspective view of a bone anchor assembly and a spinal rodcoupled to a human spine;

FIG. 4B is a perspective exploded view of the bone anchor assembly andspinal rod of FIG. 4A;

FIG. 4C is a perspective view of a hook of the bone anchor assembly ofFIG. 4A;

FIG. 4D is a perspective view of the bone anchor assembly of FIG. 4Abeing assembled in situ; and

FIG. 4E is a perspective view of the bone anchor assembly of FIG. 4Ashown with an alternate hook attachment;

FIG. 5A is a perspective view of a bone anchor assembly and a spinal rodattached to a spine;

FIG. 5B is a perspective view of a wing of the bone anchor assembly ofFIG. 5A;

FIG. 5C is another perspective view of a wing of the bone anchorassembly of FIG. 5A;

FIG. 5D is another perspective view of a wing of the bone anchorassembly of FIG. 5A;

FIG. 5E is a side view of a wing of the bone anchor assembly of FIG. 5A;

FIG. 5F is another perspective view of a wing of the bone anchorassembly of FIG. 5A;

FIG. 5G is another perspective view of a wing of the bone anchorassembly of FIG. 5A;

FIG. 5H is a top view of a wing of the bone anchor assembly of FIG. 5Awith the angled distal portion facing in a caudal direction;

FIG. 5I is a top view of a wing of the bone anchor assembly of FIG. 5Awith the angled distal portion facing in a cephalad direction;

FIG. 6A is a cross sectional view of a wing of the bone anchor assemblyof FIG. 5A prior to being secured to a closure mechanism;

FIG. 6B is a cross sectional view of the wing of FIG. 6A secured to aclosure mechanism;

FIG. 6C is another cross sectional view of the wing of FIG. 6A securedto a closure mechanism;

FIG. 7A is a perspective view of a bone anchor assembly and a spinal rodattached to a spine;

FIG. 7B is a perspective view of a wing of the bone anchor assembly ofFIG. 7A;

FIG. 7C is another perspective view of a wing of the bone anchorassembly of FIG. 7A;

FIG. 7D is a side view of a wing of the bone anchor assembly of FIG. 7A;

FIG. 7E is a top view of a wing of the bone anchor assembly of FIG. 7Awith the angled distal portion facing in a cephalad direction;

FIG. 7F is a top view of a wing of the bone anchor assembly of FIG. 7Awith the angled distal portion facing in a caudal direction;

FIG. 8A is a perspective view of a wing of bone anchor assembly;

FIG. 8B is a side view of the wing of FIG. 8A;

FIG. 8C is another side view of the wing of FIG. 8A;

FIG. 8D is a sectional side view of the wing of FIG. 8A; and

FIG. 8E is another sectional side view of the wing of FIG. 8A.

DETAILED DESCRIPTION

Bone anchor assemblies are disclosed herein that can provide forimproved fixation as compared with traditional bone anchor assemblies.An exemplary assembly can include a bracket or wing that extends downfrom the receiver member and accommodates one or more auxiliary boneanchors that augment the fixation of the assembly's primary bone anchor.Another exemplary assembly can include a plate that is seated betweenthe receiver member and the rod and accommodates one or more auxiliarybone anchors that augment the fixation of the assembly's primary boneanchor. Another exemplary assembly can include a hook that extends outfrom the receiver member to hook onto an anatomical structure or anotherimplant to augment the fixation of the assembly's primary bone anchor.Surgical methods using the bone anchor assemblies described herein arealso disclosed.

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the systems and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those skilled in the art will understand that the systems andmethods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments.

Prior Art Bone Anchor Assembly

FIGS. 1A-1C illustrate a prior art bone anchor assembly 100 with variousfeatures that can be included in the bone anchor assemblies 200, 300,400, and 500 described below. It will be appreciated that theillustrated bone anchor assembly 100 is exemplary and that the boneanchor assemblies 200, 300, 400, and 500 can include additional oralternative features.

The illustrated bone anchor assembly 100 includes a bone anchor 102, areceiver member 104 for receiving a spinal fixation element, such as aspinal rod 106, to be coupled to the bone anchor 102, and a closuremechanism 108 to capture a spinal fixation element within the receivermember and fix the spinal fixation element with respect to the receivermember. The bone anchor 102 includes a proximal head 110 and a distalshaft 112 configured to engage bone. The receiver member 104 has aproximal end having a pair of spaced apart arms 114A, 114B defining arecess 116 therebetween and a distal end having a distal end surfacedefining an opening through which at least a portion of the bone anchor102 extends. The closure mechanism 108 can be positionable between andcan engage the arms 114A, 114B to capture a spinal fixation element,e.g., a spinal rod 106, within the receiver member 104 and fix thespinal fixation element with respect to the receiver member.

The proximal head 110 of the bone anchor 102 is generally in the shapeof a truncated sphere having a planar proximal surface and anapproximately spherically-shaped distal surface. The illustrated boneanchor assembly 100 is a polyaxial bone screw designed for posteriorimplantation in the pedicle or lateral mass of a vertebra. The proximalhead 110 of the bone anchor 102 engages the distal end of the receivermember 104 in a ball and socket like arrangement in which the proximalhead and the distal shaft 112 can pivot relative to the receiver member.The distal surface of the proximal head 110 of the bone anchor 102 and amating surface within the distal end of the receiver member 104 can haveany shape that facilitates this arrangement, including, for example,spherical (as illustrated), toroidal, conical, frustoconical, and anycombinations of these shapes.

The distal shaft 112 of the bone anchor 102 can be configured to engagebone and, in the illustrated embodiment, includes an external boneengaging thread. The thread form for the distal shaft 112, including thenumber of threads, the pitch, the major and minor diameters, and thethread shape, can be selected to facilitate connection with bone.Exemplary thread forms are disclosed in U.S. Patent ApplicationPublication No. 2011/0288599, filed on May 18, 2011, and in U.S. PatentApplication Publication No. 2013/0053901, filed on Aug. 22, 2012, bothof which are hereby incorporated by reference herein. The distal shaft112 can also include other structures for engaging bone, including ahook. The distal shaft 112 of the bone anchor 102 can be cannulated,having a central passage or cannula extending the length of the boneanchor to facilitate delivery of the bone anchor over a guidewire in,for example, minimally-invasive procedures. Other components of the boneanchor assembly 100, including, for example, the closure mechanism 108,the receiver member 104, and the compression member or cap 118(discussed below) can be cannulated or otherwise have an opening topermit delivery over a guidewire. The distal shaft 112 can also includeone or more sidewall openings or fenestrations that communicate with thecannula to permit bone in-growth or to permit the dispensing of bonecement or other materials through the bone anchor 102. The sidewallopenings can extend radially from the cannula through the sidewall ofthe distal shaft 112. Exemplary systems for delivering bone cement tothe bone anchor assembly 100 and alternative bone anchor configurationsfor facilitating cement delivery are described in U.S. PatentApplication Publication No. 2010/0114174, filed on Oct. 29, 2009, whichis hereby incorporated by reference herein. The distal shaft 112 of thebone anchor 102 can also be coated with materials to permit bone growth,such as, for example, hydroxyapatite, and the bone anchor assembly 100can be coated partially or entirely with anti-infective materials, suchas, for example, tryclosan.

The proximal end of the receiver member 104 includes a pair of spacedapart arms 114A, 114B defining a U-shaped recess 116 therebetween forreceiving a spinal fixation element, e.g., a spinal rod 106. Each of thearms 114A, 114B can extend from the distal end of the receiver member104 to a free end. The outer surfaces of each of the arms 114A, 114B caninclude a feature, such as a recess, dimple, notch, projection, or thelike, to facilitate connection of the receiver member 104 toinstruments. For example, the outer surface of each arm 114A, 114B caninclude an arcuate groove at the respective free end of the arms. Suchgrooves are described in more detail in U.S. Pat. No. 7,179,261, issuedon Feb. 20, 2007, which is hereby incorporated by reference herein.

The distal end of the receiver member 104 includes a distal end surfacewhich is generally annular in shape defining a circular opening throughwhich at least a portion of the bone anchor 102 extends. For example,the distal shaft 112 of the bone anchor 102 can extend through theopening.

The bone anchor 102 can be selectively fixed relative to the receivermember 104. Prior to fixation, the bone anchor 102 is movable relativeto the receiver member 104 within a cone of angulation generally definedby the geometry of the distal end of the receiver member and theproximal head 110 of the bone anchor 102. The bone anchor assembly 100can be a favored angle screw, for example as disclosed in U.S. Pat. No.6,974,460, issued on Dec. 13, 2005, and in U.S. Pat. No. 6,736,820,issued on May 18, 2004, both of which are hereby incorporated byreference herein. Alternatively, the bone anchor assembly 100 can be aconventional (non-biased) polyaxial screw in which the bone anchor 102pivots in the same amount in every direction.

The spinal fixation element, e.g., the spinal rod 106, can eitherdirectly contact the proximal head 110 of the bone anchor 102 or cancontact an intermediate element, e.g., a compression member 118. Thecompression member 118 can be positioned within the receiver member 104and interposed between the spinal rod 106 and the proximal head 110 ofthe bone anchor 102 to compress the distal outer surface of the proximalhead into direct, fixed engagement with the distal inner surface of thereceiver member 104. The compression member 118 can include a pair ofspaced apart arms 120A and 120B defining a U-shaped seat 122 forreceiving the spinal rod 106 and a distal surface for engaging theproximal head 110 of the bone anchor 102.

The proximal end of the receiver member 104 can be configured to receivea closure mechanism 108 positionable between and engaging the arms 114A,114B of the receiver member. The closure mechanism 108 can be configuredto capture a spinal fixation element, e.g., a spinal rod 106, within thereceiver member 104, to fix the spinal rod relative to the receivermember, and to fix the bone anchor 102 relative to the receiver member.The closure mechanism 108 can be a single set screw having an outerthread for engaging an inner thread provided on the arms 114A, 114B ofthe receiver member 104. In the illustrated embodiment, however, theclosure mechanism 108 includes an outer set screw 124 operable to act onthe compression member 118 and an inner set screw 126 operable to act onthe rod 106. The receiver member 104 can include, can be formedintegrally with, or can be coupled to one or more extension tabs 128(shown in FIG. 1C) that extend proximally from the receiver member 104to functionally extend the length of the arms 114A, 114B. The extensiontabs 128 can facilitate installation and assembly of a fixation orstabilization construct and can be removed prior to completing asurgical procedure.

The bone anchor assembly 100 can be used with a spinal fixation elementsuch as rigid spinal rod 106. Alternatively, the spinal fixation elementcan be a dynamic stabilization member that allows controlled mobilitybetween the instrumented vertebrae.

In use, the bone anchor assembly 100 can be assembled such that thedistal shaft 112 extends through the opening in the distal end of thereceiver member 104 and the proximal head 110 of the bone anchor 102 isreceived in the distal end of the receiver member 104. A driverinstrument can be fitted with the bone anchor 102 to drive the boneanchor into bone. The compression member 118 can be positioned withinthe receiver member 104 such that the arms 120A, 120B of the compressionmember are aligned with the arms 114A, 114B of the receiver member 104and the lower surface of the compression member 118 is in contact withthe proximal head 110 of the bone anchor 102. A spinal fixation element,e.g., the spinal rod 106, can be located in the recess 116 of thereceiver member 104. The closure mechanism 108 can be engaged with theinner thread provided on the arms 114A, 114B of the receiver member 104.A torsional force can be applied to the outer set screw 124 to move itwithin the recess 116 so as to force the compression member 118 onto theproximal head 110 of the bone anchor 102, thereby locking the angularposition of the bone anchor 102 relative to the receiver member 104. Atorsional force can be applied to the inner set screw 126 to force thespinal rod 106 into engagement with the compression member 118 andthereby fix the spinal rod 106 relative to the receiver member 104.

The bone anchor assemblies 200, 300, 400, and 500 described below can beconfigured to operate in conjunction with, or can include any of thefeatures of, bone anchor assemblies of the type described above or othertypes known in the art. Exemplary bone anchor assemblies includemonoaxial screws, polyaxial screws, uniplanar screws, favored-anglescrews, and/or any of a variety of other bone anchor types known in theart. Further information on favored-angle screws can be found in U.S.Patent Application Publication No. 2013/0096618, filed on Oct. 9, 2012,which is hereby incorporated by reference herein.

Multipoint Fixation Implants

FIGS. 2A-2M illustrate an exemplary embodiment of a bone anchor assembly200, shown with a spinal rod 206. As noted above, a bone anchor cansometimes be inserted in a compromised state. This can be undesirable,especially in the cervical region of the spine where there is limitedbone area in which to install additional bone anchors. The illustratedbone anchor assembly 200 can allow for supplemental fixation of aprimary bone anchor in a compact footprint, without necessarilyrequiring removal or re-insertion of the primary bone anchor. As shown,the bone anchor assembly 200 can include a bone anchor 202, a receivermember 204, a closure mechanism 208, a bracket or wing 230, a nut 232,and one or more auxiliary bone anchors 234. In use, the wing 230 can besecured to the receiver member 204, e.g., using the closure mechanism208 and nut 232, thereby providing the ability to augment fixation ofthe bone anchor 202 with the one or more auxiliary bone anchors 234.

Except as described below or as will be readily appreciated by onehaving ordinary skill in the art, the bone anchor 202 and receivermember 204 are substantially similar to the bone anchor 102 and receivermember 104 described above. A detailed description of the structure andfunction thereof is thus omitted here for the sake of brevity. The boneanchor assembly 200 can include any one or more of the features of thebone anchor assembly 100 described above.

The closure mechanism 208 can be selectively secured to the receivermember 204 to capture a spinal fixation element, e.g., a spinal rod 206,within the receiver member. Tightening or locking the closure mechanism208 can be effective to fix the spinal rod 206 relative to the receivermember 204, and to fix an angular position of the bone anchor 202relative to the receiver member 204. The illustrated closure mechanism208 is in the form of a threaded post with an enlarged-diameter distalportion 208 d and a reduced-diameter proximal portion 208 p. In otherembodiments, the proximal and distal portions 208 p, 208 d can have thesame diameter, or the proximal portion can have a diameter greater thanthat of the distal portion. The distal portion 208 d of the closuremechanism 208 can be threaded into the receiver member 204 to engage aspinal rod 206 disposed in the receiver member. The proximal portion 208p of the closure mechanism 208 can protrude above the receiver member204, e.g., above a proximal-facing terminal end surface of the receivermember, and through an opening 236 formed in the wing 230, as describedfurther below.

In the illustrated embodiment, the closure mechanism 208 bears directlyagainst the spinal rod 206, which in turn bears directly against thehead of the bone anchor 202. It will be appreciated, however, that oneor more intermediate elements can also be included in the bone anchorassembly 200. For example, the bone anchor assembly 200 can include acompression member of the type described above disposed between thespinal rod 206 and the head of the bone anchor 202. The closuremechanism 208 can be a single set screw as shown, or can include anouter set screw operable to act on a compression member and an inner setscrew operable to act on the rod 206. The closure mechanism 208 caninclude a driving interface (e.g., torx, flathead, Phillips head,square, or otherwise) to facilitate rotational advancement or retractionof the closure mechanism relative to the receiver member 204 using adriver instrument.

The nut 232 can include a central opening 238 sized to receive at leasta portion of the proximal end 208 p of the closure mechanism 208therethrough. The central opening 238 can include an internal threadthat corresponds to the external thread of the closure mechanism 208,such that the nut 232 can be threaded onto the closure mechanism andtightened to secure the wing 230 to the closure mechanism and thereceiver member 204 in which the closure mechanism is disposed. Theouter surface of the nut 232 can be faceted or otherwise configured tofacilitate application of torque to the nut. In some embodiments, thenut 232 can have a hexagonal or square cross-section.

As shown in FIGS. 2E-2H, the bracket or wing 230 can include a proximalportion 230 p that can contact the receiver member 204, a distal portion230 d that can contact a bone surface or be disposed in close proximityto a bone surface, and a spanning portion 230 s that connects theproximal and distal portions.

The proximal portion 230 p of the wing 230 can include a central opening236 sized to receive at least a portion of the closure mechanism 208therethrough. For example, the central opening 236 can be sized toreceive the proximal portion 208 p of the closure mechanism 208therethrough. The central opening 236 can include a smooth, non-threadedinterior surface to allow the wing 230 and the closure mechanism 208 tobe freely rotatable with respect to one another. A proximal-facingsurface 240 of the proximal portion 230 p of the wing 230 can be domedor rounded to provide an atraumatic surface and reduce the risk oftissue irritation post-implantation. A distal-facing surface 242 of theproximal portion 230 p of the wing 230 can be configured to engage theproximal-facing surface of the receiver member 204. The distal-facingsurface 242 can form a negative or a substantial negative of theproximal-facing surface of the receiver member 204. For example, theproximal-facing surfaces of the arms 214A, 214B of the receiver member204 can be radially-convex, and the distal-facing surface 242 of thewing 230 can define a radially-concave channel that receives the convexends of the arms. In some embodiments, the central opening 236 oranother feature of the wing 230 can be sized and configured to snap ontoor capture a portion of the closure mechanism 208 or a proximal surfaceof the receiver member 204.

The distal portion 230 d of the wing 230 can include one or moreopenings 244 configured to receive a bone anchor 234 therethrough. Whiletwo bone anchor openings 244 are shown in the illustrated embodiment, itwill be appreciated that the wing 230 can include any number of boneanchor openings (e.g., one, two, three, four, five, and so on). The boneanchor openings 244 can include any of a number of features foraccepting bone anchors 234 at varying angles and/or increasing thesecurity and stability with which bone anchors can be secured to thewing 230. Exemplary features that can be included are disclosed in U.S.Pat. No. 7,637,928, issued on Dec. 29, 2009; U.S. Pat. No. 8,343,196,issued on Jan. 1, 2013; U.S. Pat. No. 8,574,268, issued on Nov. 5, 2013;U.S. Pat. No. 8,845,697, issued on Sep. 30, 2014; and U.S. Pat. No.8,758,346, issued on Jun. 24, 2014, which are each hereby incorporatedby reference herein. For example, the bone anchor openings 244 can be atleast partially threaded to receive a variable-angle locking screwhaving a threaded proximal head. As shown, the openings 244 can have aplurality of columns of threads spaced apart to define a plurality ofnon-threaded recesses. In the illustrated embodiment, each of theopenings 244 has four columns of threads. The columns of threads can bearranged around the inner surface of each of the openings 244 forengaging threads on the heads of locking auxiliary bone anchors and/orvariable-angle locking auxiliary bone anchors. The auxiliary boneanchors 234 can thus be locked with the wing 230 coaxially with thecentral axis of the opening 244 or at a selected angle within a range ofselectable angles relative to the central axis of the opening. Theauxiliary bone anchors 234 can include features to facilitate thisvariable-angle locking, such as a proximal head that is at leastpartially spherical having a thread with a profile that follows thearc-shaped radius of curvature of the spherical portion of the head. Thevariable-angle capability of the screw/opening interface can allow theuser to place locking auxiliary bone anchors into the bone at any anglewithin defined angulation limits, thus providing improved placementflexibility and eliminating or reducing the need to conform the distalportion of the wing to the bone surface to achieve a desired insertionangle. The auxiliary bone anchors 234 can be driven into the bone withdiverging or converging longitudinal axes (relative to each other and/orrelative to the primary bone anchor 202) which can provide improvedresistance to pullout. In some embodiments, the interior surfaces of theopenings 244 can be smooth or spherical, without threads or lockingfeatures.

The central axis of each of the openings 244 can be perpendicular orsubstantially perpendicular to a distal-facing surface 246 of the wing230. Alternatively, one or more of the openings can have a central axisthat extends at an oblique angle with respect to the distal-facingsurface 246. In the illustrated embodiment, the central axis of eachopening 244 extends at an angle of about 7 degrees with respect to thedistal-facing surface 246. In some embodiments, the central axis of eachopening 244 can extend at an angle of between about 0 degrees and about15 degrees with respect to the distal-facing surface 246 (e.g.,embodiments used for bony attachment locations that allow directproximal to distal screw insertion). In some embodiments, the centralaxis of each opening 244 can extend at an angle of between about 15degrees and about 45 degrees with respect to the distal-facing surface246 (e.g., embodiments used for bony attachment locations where anangled trajectory may avoid or target specific anatomy). Angled ordivergent central axes can advantageously increase the pulloutresistance of the construct.

The distal portion 230 d of the wing 230 can have a distal-facingsurface 246 configured to contact bone or to be disposed in closeproximity to bone. The distal-facing surface 246 can include teeth,texturing, or other surface features to enhance grip with the adjacentbone. The distal portion 230 d of the wing 230 can have a lateralsurface 248 that abuts a sidewall of the receiver member 204. Thelateral surface 248 can form a negative of the sidewall of the receivermember 204, such that the distal-portion 230 d of the wing 230 can hugthe receiver member with minimal or zero gap therebetween. For example,the lateral surface 248 can be concave with a radius of curvature equalor substantially equal to a radius of curvature of the exterior sidewallof the receiver member 204.

The spanning portion 230 s of the wing 230 can extend vertically in aproximal-distal direction to join the proximal portion 230 p of the wingto the distal portion 230 d of the wing. The spanning portion 230 s ofthe wing 230 can have a lateral surface 250 that engages a sidewall ofthe receiver member 204. The lateral surface 250 can form a negative ofthe sidewall of the receiver member 204, such that the spanning portion230 s of the wing 230 can hug the receiver member with minimal or zerogap therebetween. For example, the lateral surface 250 can be concavewith a radius of curvature equal or substantially equal to a radius ofcurvature of the exterior sidewall of the receiver member 204. Thelateral surface 250 can also include one or more protrusions 252 forengaging a corresponding recess 254 formed in the sidewall of thereceiver member 204, or one or more recesses in which a protrusion ofthe receiver member is received. The interaction between the one or moreprotrusions 252 and the one or more recesses 254 can be effective tolimit or prevent rotation of the wing 230 with respect to the receivermember 204. This interaction can also be effective to limit or preventmovement of the wing 230 with respect to the receiver member 204 along aproximal-distal axis. The spanning portion 230 s can include webbing orribs 256 to enhance the structural rigidity of the wing 230. The ribs256 can be formed in an outer surface of the spanning portion 230 s,opposite to the lateral surface 250 that engages the receiver member204.

The proximal portion 230 p, distal portion 230 d, and spanning portion230 s can be formed integrally as a monolithic unit as shown, or one ormore of said components can be separate and selectively attachable tothe others. In some embodiments, a kit of modular components can beprovided to allow selection of the components most appropriate for agiven use. For example, a spanning portion 230 s of appropriate heightcan be selected based on the distance between the proximal end of thereceiver member 204 and the bone surface in a given application.

One or more portions of the wing 230 can be flexible or deformable toallow the wing to be custom-tailored for a particular situation.

For example, the distal portion 230 d of the wing 230 can be flexible ordeformable to allow the distal portion to be contoured to the bonesurface. The distal portion 230 d can be contoured before implantationor in situ. The distal portion 230 d can be contoured using a separatebending instrument, or by tightening the bone anchors 234 to deform thedistal portion into intimate contact with the bone surface. The distalportion 230 d of the wing 230 can be pre-shaped or pre-contoured, e.g.,during manufacture, to match a bone surface with which the bone anchorassembly 200 is to be used.

By way of further example, the spanning portion 230 s of the wing 230can be flexible or deformable to allow the position of the bone anchoropenings 244 to be adjusted relative to the receiver member 204. Thespanning portion 230 s can be bent or flexed inwardly or outwardly(e.g., in a medial-lateral direction) to move the bone anchor openings244 inward towards the receiver member 204 or outward away from thereceiver member. Such bending can also increase or decrease theeffective height of the wing 230, to accommodate varying distances thatmay be encountered between the proximal end of the receiver member 204and the bone surface. The spanning portion 230 s can be bent or flexedup or down (e.g., in a superior-inferior direction) to move the boneanchor openings 244 relative to the receiver member 204. The spanningportion 230 s can be contoured before implantation or in situ. Thespanning portion 230 s can be contoured using a separate bendinginstrument, or by tightening the bone anchors 234 to deform the spanningportion into the desired shape. The spanning portion 230 s of the wing230 can be pre-shaped or pre-contoured, e.g., during manufacture, for agiven application.

As yet another example, the proximal portion 230 p of the wing 230 canbe flexible or deformable, and/or the connections or locations at whichthe proximal portion 230 p, the distal portion 230 d, and the spanningportion 230 s are joined can be flexible or deformable. The proximalportion 230 p, distal portion 230 d, and spanning portion 230 s can bejoined by a living hinge or other joint to allow adjustment to theirrelative positions.

The spanning portion 230 s can have an adjustable height. For example,as shown in FIGS. 2I-2M, the spanning portion 230 s can include firstand second flexible or deformable legs 258. By bending the legs 258inward towards one another, the height of the spanning portion 230 s canbe increased. By bending the legs 258 outward away from one another, theheight of the spanning portion 230 s can be decreased. Each leg 258 caninclude an upper portion and a lower portion joined by a flexible joint(e.g., a living hinge, pivot pin, or the like). Rounded or semi-circularsurfaces can be formed at the connections between the legs 258 and theproximal and distal portions 230 p, 230 d of the wing 230 to reducematerial stress as the legs are bent. Similarly, a rounded orsemi-circular cut-out can be formed where the upper portion of each leg258 meets the lower portion. The cut-out can reduce stress and alsoprovide an engagement surface for gripping the legs 258 with a toolconfigured to apply a squeezing force thereto.

The bone anchor assembly 200 can provide significant flexibility for thesurgeon. The wing 230 can be easily flipped around to be positioned oneither side of the rod 206 (e.g., on a medial side or a lateral side ofthe rod). The wing 230 can be freely rotated about the closure mechanism208 prior to final locking of the wing to the receiver member 204,allowing the auxiliary bone anchor holes 244 to be positioned at variouslocations with respect to the spinal rod 206, as shown in FIG. 2D. Asdescribed in detail above, the wing 230 can be deformable or flexible,or can include deformable or flexible portions, to allow the wing to fitsnugly with the receiver member 204, to match a contour of the bonesurface, to reposition the auxiliary bone anchor holes 244 with respectto the receiver member, and/or to adjust a height of the wing toaccommodate receiver members of different heights or situations wherethe primary bone anchor 202 is over or under inserted into the bone.

Referring again to FIG. 2A, the proximal-most extent of each auxiliarybone anchor 234 can be distal to the spinal rod 206. In otherembodiments, the proximal-most extent of each auxiliary bone anchor 234can be distal to the distal-most extent of the receiver member 204.These configurations can advantageously reduce the overall profile ofthe assembly 200. The wing 200 can be Z-shaped or substantiallyZ-shaped.

The wing 230 can extend radially outward from the receiver member 204(e.g., by a distance equal to the width of the distal portion 230 d ofthe wing). The degree to which the wing 230 extends outward from thereceiver member 204 can vary among different embodiments. In theillustrated embodiment, the ratio of wing extension to rod diameter (orthe ratio of wing extension to the width of the rod-receiving recess inthe receiver member) is about 2:1. In some embodiments, this ratio canbe less than about 10:1, less than about 5:1, less than about 3:1, lessthan about 2:1, less than about 1:1, and/or less than about 0.5:1. Insome embodiments, the ratio can be about 10:1, about 5:1, about 3:1,about 2:1, about 1:1, or about 0.5:1.

The centers of the auxiliary bone anchor holes 244 (and thus at least aportion of the auxiliary bone anchors 234 disposed therein) can bespaced radially apart from the center of the opening in the receivermember 204 in which the primary bone anchor 202 is disposed. In someembodiments, this spacing can be less than about 2.5 times the diameterof the receiver member 204. In some embodiments, this spacing can beless than about 2 times the diameter of the receiver member 204. In someembodiments, this spacing can be less than the diameter of the receivermember 204. In some embodiments, this spacing can be between about 5 mmand about 10 mm. In some embodiments, this spacing can be about 7.5 mm.In some embodiments, the auxiliary bone anchors 234 can be containedwithin an envelope no bigger than 2.5 times the diameter of the receivermember 204. In some embodiments, the auxiliary bone anchors 234 can becontained within an envelope no bigger than 2 times the diameter of thereceiver member 204.

The auxiliary bone anchors 234 can include any of the features of thebone anchor 202 described above, and any of a variety of other bonescrews or other anchors can be used instead or in addition. As notedabove, the auxiliary bone anchors 234 can have threaded proximal headsto facilitate variable-angle locking with the wing 230. In someembodiments, the auxiliary bone anchors 234 can have a length of about 6mm to about 20 mm (e.g., in embodiments used for cervical applications).In some embodiments, the auxiliary bone anchors 234 can have a length ofabout 6 mm to about 100 mm (e.g., in embodiments used for lumbar orsacral applications). The length of the auxiliary bone anchors 234 canbe selected based on various factors, including the available safe boneat any given attachment location. The auxiliary bone anchors 234 canhave a length equal to that of the primary bone anchor 202. Theauxiliary bone anchors 234 can have a length less than that of theprimary bone anchor 202. The auxiliary bone anchors 234 can have alength that is between about 60% and about 80% of the length of theprimary bone anchor 202. The auxiliary bone anchors 234 can have alength that is about 70% of the length of the primary bone anchor 202.The auxiliary bone anchors 234 can have a length of about 10 mm. Theauxiliary bone anchors 234 can have a length of about 14 mm. In someembodiments, two 10 mm auxiliary bone anchors can be used with one 14 mmprimary bone anchor. In some embodiments, one 14 mm auxiliary boneanchor can be used with one 14 mm primary bone anchor. The auxiliarybone anchors 234 can have a shank diameter equal to that of the primarybone anchor 202. The auxiliary bone anchors 234 can have a shankdiameter less than that of the primary bone anchor 202. The auxiliarybone anchors 234 can have a shank diameter that is between about 50% andabout 70% of the shank diameter of the primary bone anchor 202. Theauxiliary bone anchors 234 can have a shank diameter that is about 60%of the shank diameter of the primary bone anchor 202.

FIGS. 3A-3I illustrate an exemplary embodiment of a bone anchor assembly300, shown with a spinal rod 306. As shown, the bone anchor assembly 300can include a bone anchor 302, a receiver member 304, a closuremechanism 308, a grommet or plate 360, and one or more auxiliary boneanchors 334. In use, a saddle portion of the plate can be disposedbetween the rod 306 and the receiver member 304 to secure the plate 360to the receiver member, thereby providing the ability to augmentfixation of the bone anchor 302 with the one or more auxiliary boneanchors 334.

Except as described below or as will be readily appreciated by onehaving ordinary skill in the art, the bone anchor 302, receiver member304, and closure mechanism 308 are substantially similar to the boneanchor 102, receiver member 104, and closure mechanism 108 describedabove. A detailed description of the structure and function thereof isthus omitted here for the sake of brevity. The bone anchor assembly 300can include any one or more of the features of the bone anchor assembly100 described above.

As shown in FIGS. 3C-3F, the grommet or plate 360 can include a primaryopening 362 configured to receive at least a portion of the receivermember 304 therethrough. The plate can also include one or more openings364 configured to receive a bone anchor 334 therethrough. While a singlebone anchor opening 364 is shown in the illustrated embodiment, it willbe appreciated that the plate 360 can include any number of bone anchoropenings (e.g., one, two, three, four, five, and so on). The bone anchoropenings 364 can include any of a number of features for accepting boneanchors 334 at varying angles and/or increasing the security andstability with which bone anchors can be secured to the plate 360.Exemplary features that can be included are disclosed in U.S. Pat. No.7,637,928, issued on Dec. 29, 2009; U.S. Pat. No. 8,343,196, issued onJan. 1, 2013; U.S. Pat. No. 8,574,268, issued on Nov. 5, 2013; U.S. Pat.No. 8,845,697, issued on Sep. 30, 2014; and U.S. Pat. No. 8,758,346,issued on Jun. 24, 2014, which are each hereby incorporated by referenceherein. For example, the bone anchor opening 364 can be at leastpartially threaded to receive a variable-angle locking screw having athreaded proximal head. As shown, the opening 364 can have a pluralityof columns of threads spaced apart to define a plurality of non-threadedrecesses. In the illustrated embodiment, the opening 364 has fourcolumns of threads. The columns of threads can be arranged around theinner surface of the opening 364 for engaging threads on the heads oflocking auxiliary bone anchors and/or variable-angle locking auxiliarybone anchors. The auxiliary bone anchor 334 can thus be locked with theplate 360 coaxially with the central axis of the opening 364 or at aselected angle within a range of selectable angles relative to thecentral axis of the opening. The auxiliary bone anchor 334 can includefeatures to facilitate this variable-angle locking, such as a proximalhead that is at least partially spherical having a thread with a profilethat follows the arc-shaped radius of curvature of the spherical portionof the head. The variable-angle capability of the screw/openinginterface can allow the user to place locking auxiliary bone anchorsinto the bone at any angle within defined angulation limits, thusproviding improved placement flexibility and eliminating or reducing theneed to conform the plate to the bone surface to achieve a desiredinsertion angle. The auxiliary bone anchor 334 can be driven into thebone with a diverging or converging longitudinal axis relative to theprimary bone anchor 302 and/or relative to other auxiliary bone anchors334, which can provide improved resistance to pullout. In someembodiments, the interior surface of the opening 334 can be smooth orspherical, without threads or locking features.

The central axis of the opening 364 can be perpendicular orsubstantially perpendicular to a distal-facing surface of the plate 360.Alternatively, the opening 364 can have a central axis that extends atan oblique angle with respect to the distal-facing surface. In theillustrated embodiment, the central axis of the opening 364 extends atan angle of about 0 degrees with respect to the distal-facing surface.In some embodiments, the central axis of the opening 364 can extend atan angle of between about 0 degrees and about 15 degrees with respect tothe distal-facing surface (e.g., embodiments used for bony attachmentlocations that allow direct proximal to distal screw insertion). In someembodiments, the central axis of the opening 364 can extend at an angleof between about 15 degrees and about 45 degrees with respect to thedistal-facing surface (e.g., embodiments used for bony attachmentlocations where an angled trajectory may avoid or target specificanatomy). An angled or divergent central axis can advantageouslyincrease the pullout resistance of the construct.

The plate 360 can include a saddle portion 366 that extends across atleast a portion of the primary opening 362. The saddle portion 366 canspan entirely across the primary opening 362, or can be cantilevered asshown to project out across the opening without contacting the oppositeside of the opening. The latter configuration can advantageouslyfacilitate bending of the saddle portion 366 with respect to the rest ofthe plate 360, thereby allowing the position of the plate with respectto the receiver member 304 to be adjusted (e.g., to bend the plate downinto contact with the bone surface). The saddle portion 366 can includea distal facing surface 366 d that mimics the distal facing surface of aspinal fixation or stabilization element with which the bone anchorassembly 300 is to be used. For example, in the case of a cylindricalspinal rod 306, the distal-facing surface 366 d of the saddle portion366 can define a section of a cylinder having a radius equal to orsubstantially equal to the diameter of the spinal rod. Theproximal-facing surface 366 p of the saddle portion 366 can define aseat configured to receive the spinal fixation or stabilization elementtherein. In the illustrated embodiment, the seat 366 p is sized andshaped to receive a cylindrical spinal rod 306 therein. The radius ofcurvature of the proximal-facing seat 366 p can be equal to orsubstantially equal to that of the rod-receiving channel of the receivermember 304.

The saddle portion 366 can effectively divide the primary opening 362into first and second openings on either side of the saddle portion,each sized to receive a corresponding one of the arms 314A, 314B of thereceiver member 304. When assembled, the opposed arms 314A, 314B of thereceiver member can be inserted through the first and second openingssuch that the plate 360 surrounds the receiver member 304 and such thatthe saddle portion 366 is seated within the rod-receiving recess of thereceiver member. The spinal rod 306 can then be seated on theproximal-facing surface 366 p of the saddle portion 366, between theopposed arms 314A, 314B of the receiver member 304, and locked in placewith the closure mechanism 308 as described above, thereby also lockingthe plate 360 to the receiver member. An auxiliary bone anchor 334 canbe inserted through each of the one or more bone anchor openings 364 inthe plate to augment the fixation provided by the primary bone anchor302.

The primary opening 362 in the plate can be defined by a first sidewall368 that is generally ring-shaped and that intersects with a secondsidewall 370 that is also generally ring-shaped and that defines the oneor more auxiliary bone anchor openings 364. The height of the firstsidewall 368 can be reduced at the junction with the second sidewall 370or in areas adjacent thereto to facilitate bending of the plate 360 toreposition the auxiliary bone anchor opening 364 with respect to thereceiver member 304.

The first and second sidewalls 368, 370 can be formed integrally as amonolithic unit as shown, or one or more of said components can beseparate and selectively attachable to the other. In some embodiments, akit of modular components can be provided to allow selection of thecomponents most appropriate for a given use. For example, a firstsidewall 368 of appropriate size can be selected based on the size ofthe receiver member 304 or the size of the spinal rod 306. By way offurther example, one or more modular second sidewalls 370 can beattached to the first sidewall 368, e.g., depending on the number ofauxiliary bone anchors 334 that are to be used.

The second sidewall 370, and thus the auxiliary bone anchor opening 364defined thereby, can be positioned at any of a variety of locationsabout the perimeter of the first sidewall 368. In the illustratedembodiment, for example, the auxiliary bone anchor opening 364 ispositioned approximately at a “5 o'clock” or “lower” position withrespect to the saddle portion 366, such that the center point of theauxiliary bone anchor opening 364 is offset laterally from the saddleportion and aligned with an inferior end of the saddle portion. In otherembodiments, the auxiliary bone anchor opening 364 can be positionedapproximately at a “3 o'clock” or “middle” position with respect to thesaddle portion 366, such that the center point of the auxiliary boneanchor opening 364 is offset laterally from the saddle portion andaligned with a longitudinal midpoint of the saddle portion. In otherembodiments, the auxiliary bone anchor opening 364 can be positionedapproximately at a “1 o'clock” or “upper” position with respect to thesaddle portion 366, such that the center point of the auxiliary boneanchor opening 364 is offset laterally from the saddle portion andaligned with a superior end of the saddle portion. A kit can be providedincluding a plurality of plates 360, each including auxiliary boneanchor openings 364 positioned at different locations with respect tothe saddle portion 366, to give the user flexibility in locating theauxiliary bone anchor 334 relative to the rod 306. This can allow theuser to select a plate 360 that will position the auxiliary bone anchor334 in a good position to get bone purchase.

One or more portions of the plate 360 can be flexible or deformable toallow the plate to be custom-tailored for a particular situation. Forexample, as noted above, the portion of the plate 360 in which the boneanchor opening(s) 364 are formed can be bent or flexed to repositionsaid portion with respect to the portion of the plate in which thereceiver member 304 is disposed. The plate 360 can be contoured beforeimplantation or in situ. The plate 360 can be contoured using a separatebending instrument, or by tightening the bone anchors 334 to deform theplate into intimate contact with the bone surface. The plate 360 can bepre-shaped or pre-contoured, e.g., during manufacture, to match a bonesurface or construct with which the bone anchor assembly 300 is to beused.

In some cases, the thickness of the saddle portion 366 can cause thespinal rod 306 to be raised up within the receiver member 304 to adegree that prevents sufficient attachment of the closure mechanism 308or prevents attachment of the closure mechanism altogether. In suchcases, the bone anchor assembly 300 can include a cap 372, e.g., of thetype shown in FIG. 3H. The cap 372 can attach to the proximal end of thereceiver member 304. The cap 372 can include a threaded central openingsized to receive the closure mechanism 308. Accordingly, the cap 372 canfunctionally extend the height of the threaded portion of the receivermember 304 to accommodate both the rod 306 and the saddle portion 366between the rod-receiving channel of the receiver member 304 and theclosure mechanism 308. The illustrated cap 372 includes a generallyU-shaped channel sized to accommodate the spinal rod 306. The cap 372can be attached to the receiver member 304 in any of a variety of ways.For example, the cap 372 can include one or more projections that engagewith a corresponding one or more recesses formed in the receiver member304, or the receiver member can include one or more projections thatengage with a corresponding one or more recesses formed in the cap. Thecap 372 can snap fit onto the receiver member 304. The cap 372 can slideonto the receiver member 304 from the side with a tongue and groove ordovetail connection. The cap 372 can lock onto the receiver member 304by a quarter-turn rotation of the cap relative to the receiver member.

The bone anchor assembly 300 can provide significant flexibility for thesurgeon. The plate 360 can be easily flipped around to be positioned oneither side of the rod 306 (e.g., on a medial side or a lateral side ofthe rod). As described in detail above, the plate 360 can be deformableor flexible, or can include deformable or flexible portions, to allowthe plate to fit snugly with the receiver member 304, to match a contourof the bone surface, to reposition the auxiliary bone anchor hole(s) 364with respect to the receiver member, and/or to adjust a height of theplate to accommodate receiver members of different heights or situationswhere the primary bone anchor 302 is over or under inserted into thebone. The bone anchor assembly 300 is shown in FIG. 3I installed as partof a multi-level spinal fixation construct. As shown, the plate 360allows an auxiliary bone anchor 334 to be installed at the samevertebral level as the primary bone anchor 302 to augment the fixationof the primary bone anchor.

Referring again to FIG. 3A, the proximal-most extent of each auxiliarybone anchor 334 can be distal to the spinal rod 306. In otherembodiments, the proximal-most extent of each auxiliary bone anchor 334can be distal to the distal-most extent of the receiver member 304.These configurations can advantageously reduce the overall profile ofthe assembly 300.

The centers of the auxiliary bone anchor hole(s) 364 (and thus at leasta portion of the auxiliary bone anchor(s) 334 disposed therein) can bespaced radially apart from the center of the opening in the receivermember 304 in which the primary bone anchor 302 is disposed. In someembodiments, this spacing can be less than about 2.5 times the diameterof the receiver member 304. In some embodiments, this spacing can beless than about 2 times the diameter of the receiver member 304. In someembodiments, this spacing can be less than the diameter of the receivermember 304. In some embodiments, this spacing can be between about 5 mmand about 10 mm. In some embodiments, this spacing can be about 7.5 mm.In some embodiments, the auxiliary bone anchors 334 can be containedwithin an envelope no bigger than 2.5 times the diameter of the receivermember 304. In some embodiments, the auxiliary bone anchors 334 can becontained within an envelope no bigger than 2 times the diameter of thereceiver member 304.

The auxiliary bone anchors 334 can include any of the features of thebone anchor 302 described above, and any of a variety of other bonescrews or other anchors can be used instead or in addition. As notedabove, the auxiliary bone anchors 334 can have threaded proximal headsto facilitate variable-angle locking with the plate 360. In someembodiments, the auxiliary bone anchors 334 can have a length of about 6mm to about 20 mm (e.g., in embodiments used for cervical applications).In some embodiments, the auxiliary bone anchors 334 can have a length ofabout 6 mm to about 100 mm (e.g., in embodiments used for lumbar orsacral applications). The length of the auxiliary bone anchors 334 canbe selected based on various factors, including the available safe boneat any given attachment location. The auxiliary bone anchors 334 canhave a length equal to that of the primary bone anchor 302. Theauxiliary bone anchors 334 can have a length less than that of theprimary bone anchor 302. The auxiliary bone anchors 334 can have alength that is between about 60% and about 80% of the length of theprimary bone anchor 302. The auxiliary bone anchors 334 can have alength that is about 70% of the length of the primary bone anchor 302.The auxiliary bone anchors 334 can have a length of about 10 mm. Theauxiliary bone anchors 334 can have a length of about 14 mm. In someembodiments, two 10 mm auxiliary bone anchors can be used with one 14 mmprimary bone anchor. In some embodiments, one 14 mm auxiliary boneanchor can be used with one 14 mm primary bone anchor. The auxiliarybone anchors 334 can have a shank diameter equal to that of the primarybone anchor 302. The auxiliary bone anchors 334 can have a shankdiameter less than that of the primary bone anchor 302. The auxiliarybone anchors 334 can have a shank diameter that is between about 50% andabout 70% of the shank diameter of the primary bone anchor 302. Theauxiliary bone anchors 334 can have a shank diameter that is about 60%of the shank diameter of the primary bone anchor 302.

The saddle portion 366 can extend completely across the rod-receivingrecess of the receiver member 304. The saddle portion 366 can extendacross less than an entirety of the rod-receiving recess of the receivermember 304 (e.g., across only a portion of the rod-receiving recess).The saddle portion 366 can be omitted altogether. For example, the plate360 can include an alternative distal facing portion to bear against thereceiver member 304 and transfer the holding force of the auxiliary boneanchors 334 to the receiver member. Exemplary distal facing portions caninclude a lip, a shelf, a face, a tapered portion, and/or teeth that canmesh or engage with a portion of the receiver member 304.

FIGS. 4A-4E illustrate an exemplary embodiment of a bone anchor assembly400, shown with a spinal rod 406. As shown, the bone anchor assembly 400can include a bone anchor 402, a receiver member 404, a closuremechanism 408, a hook 474, a washer or collar 476, and a locking screw478. In use, the collar 476 and locking screw 478 can be used to attachthe hook 474 to the receiver member 404. The hook 474 can be hooked ontoor engaged with a portion of the patient anatomy or a nearby implant toaugment fixation of the bone anchor 402.

Except as described below or as will be readily appreciated by onehaving ordinary skill in the art, the bone anchor 402, receiver member404, and closure mechanism 408 are substantially similar to the boneanchor 102, receiver member 104, and closure mechanism 108 describedabove. A detailed description of the structure and function thereof isthus omitted here for the sake of brevity. The bone anchor assembly 400can include any one or more of the features of the bone anchor assembly100 described above.

The hook 474 can include a body portion 480 with a curved or loopedextension 482 projecting therefrom.

The extension 482 can be substantially U-shaped, with an inside curvedsurface 484 and an outside curved surface 486. The extension 482 can besized and configured to hook onto a portion of the patient's anatomy(e.g., a lamina, spinous process, or other bone structure of thepatient) or onto another implant or implant construct (e.g., across-connector, screw, rod, plate, intervertebral implant, or thelike). For example, the inside curved surface 484 can form a negative ora substantial negative of the anatomy or implant.

As shown in FIG. 4A, the hook 474 can be coupled to the lamina L of thepatient such that a proximal-facing surface 488 of the inside curve 484of the extension 482 abuts a distal facing surface of the lamina andsuch that a distal-facing surface 490 of the inside curve 484 of theextension 482 abuts a proximal-facing surface of the lamina.

While a single extension 482 is shown in the illustrated embodiment, itwill be appreciated that the hook 474 can include any number ofextensions (e.g., one, two, three, four, five, and so on).

One or more portions of the hook 474 can be flexible or deformable toallow the hook to be custom-tailored for a particular situation. Forexample, the extension 482 of the hook 474 can be contoured to match theanatomy or implant onto which the extension is to be hooked. The hook474 can be contoured before implantation or in situ. The hook 474 can becontoured using a separate bending instrument, or by tightening thelocking screw 478 to deform the hook into intimate contact with theanatomy or implant. The hook 474 can be pre-shaped or pre-contoured,e.g., during manufacture, to match an anatomy or implant with which thebone anchor assembly 400 is to be used.

In some embodiments, a kit of modular hooks 474 can be provided to allowselection of the hook or hooks most appropriate for a given use. Forexample, hooks 474 having extensions 482 of varying sizes thatcorrespond to the varying sizes of laminae found in a patient populationor the varying sizes of laminae found within a single human spine can beincluded in the kit and the most appropriately sized hook can beselected for the surgery. Hooks 474 of varying size and/or varyingoffset relative to the receiver member 404 can be included in a kit.

The body portion 480 of the hook 474 can include an opening 492 forreceiving the locking screw 478 to secure the hook to the collar 476.The opening 492 can be threaded such that the locking screw 478 can bethreaded into the opening. The body portion 480 of the hook 474 caninclude a lateral surface 494 that engages a sidewall of the receivermember 404. The lateral surface 494 can form a negative of the sidewallof the receiver member 404, such that the hook 474 can hug the receivermember with minimal or zero gap therebetween. For example, the lateralsurface 494 can be concave with a radius of curvature equal orsubstantially equal to a radius of curvature of the exterior sidewall ofthe receiver member 404.

The collar 476 can include a first opening 496A sized to receive atleast a portion of the receiver member 404 therethrough and a secondopening 496B sized to receive the locking screw 478 therethrough. Thefirst and second openings 496A, 496B can intersect one another, suchthat the collar 476 defines a “snowman” or “figure eight” shaped centralopening. The collar 476 can include one or more engagement features forforming a positive interlock with the receiver member 404, which canadvantageously prevent the collar from inadvertently sliding off of thereceiver member. For example, the collar 476 can include one or moreprojections 498 that extend radially inward into the first opening 496Ato engage corresponding one or more recesses 499 formed in an exteriorsidewall of the receiver member 404. In other embodiments, the recessescan be formed in the collar 476 and the projections can be formed on thereceiver member 404. The first opening 496A can include one or moreflats (e.g., opposed parallel, planar sidewalls as shown) that mate withcorresponding one or more flats (e.g., opposed parallel, planarsidewalls) of the receiver member 404 to prevent rotation of the collar476 with respect to the receiver member.

The second opening 496B of the collar 476 can be circular orsemi-circular to accommodate the cylindrical shaft of the locking screw478. In other embodiments, the second opening 496B can be elongated toallow the locking screw 478 to be secured at any of a variety oflocations along a length of the elongated opening. This canadvantageously allow the distance between the receiver member 404 andthe hook 474 to be adjusted as desired. The second opening 496B can havea conical or tapered countersink shape as shown such that, as thelocking screw 478 is tightened, the collar 476 is pushed to the right inFIG. 4A, cinching in the receiver member 404 and locking down the entireassembly.

When assembled, the collar 476 can sit above the spinal rod 406 andextend around the outer periphery of the receiver member 404 to securethe hook 474 to the side of the receiver member. The hook 474 can behooked onto patient anatomy or another implant to augment the fixationof the bone anchor assembly 400. In some embodiments, the hook 474 canbe hooked onto an anatomical structure at the same vertebral level asthe bone anchor 402 is inserted. Thus, for example, the bone anchor 402can be advanced into the pedicle or lateral mass of a vertebra and thehook 474 can be hooked onto a lamina of that same vertebra. As shown inFIG. 4A, the collar 476 does not interfere with insertion of the closuremechanism 408 into the receiver member 404, or with tightening orloosening of the closure mechanism. In addition, the hook 474 and collar476 can be attached to the receiver member 404 after the rod 406 isinstalled in the receiver member.

The bone anchor assembly 400 can provide significant flexibility for thesurgeon. The collar 476 and hook 474 can be easily flipped around to bepositioned on either side of the rod 406 (e.g., on a medial side or alateral side of the rod). The hook 474 can be deformable or flexible, orcan include deformable or flexible portions, to allow the hook to fitsnugly with the receiver member 404, to match a contour of the bonesurface, to reposition the hook with respect to the receiver member,and/or to adjust a height of the hook to accommodate receiver members ofdifferent heights or situations where the primary bone anchor 402 isover or under inserted into the bone.

As shown in FIG. 4E, instead of using a locking screw 478 and a collar476 that wraps around the receiver member 404, the hook 474 can attachto the receiver member in a manner similar to that used to attach thewing 230 of FIGS. 2A-2M. In particular, the hook can include a proximalportion 474 p that sits atop the opposed arms 414A, 414B of the receivermember 404 and that defines a central opening through which a closuremechanism 408 in the form of an extended threaded post is received. Thehook 474 can be locked onto the closure mechanism 408 and the receivermember by a threaded nut 432.

The hook 474 can be attached to the receiver member 404 after thereceiver member and the bone anchor 402 are coupled to the bone, whichcan advantageously give the surgeon more flexibility for insertion andalso allow insertion of the bone anchor and receiver member with anunobstructed view. In addition, the hook 474 can be coupled to thereceiver member 404 such that the bone anchor 402 does not restrictmovement of the hook. The hook 474 can thus be positioned with respectto the bone anchor 402 at least with as many degrees of freedom as thereceiver member 404.

As discussed above in the embodiment of FIGS. 2A-2M, supplementalfixation of a primary bone anchor in a bone anchor assembly can beaccomplished using a wing or bracket having one or more bone anchoropenings through which one or more auxiliary bone anchors can be driveninto bone. In some instances, however, a surgeon may experiencedifficulty in making certain bone anchor placements having angulartrajectories. Variability in the bony anatomy of the spine can make itdifficult to position the distal portion of the wing in close proximityto bone to facilitate proper engagement or purchase with the anchor. Adriver instrument used to drive an auxiliary anchor into bone canrequire more clearance to access the bone anchor opening of the wing.

To address such potential difficulties in supplemental fixation ofauxiliary bone anchors, various embodiments of a bone anchor assemblyare disclosed herein that include a wing or bracket having an angleddistal portion. In some embodiments, the distal portion of the wing canbe angled to the right or left of the spanning portion of the wing tofacilitate bone anchor placements having a cephalad trajectory (i.e.,towards a patient's head) and/or a caudal trajectory (i.e., towards apatient's feet). In some embodiments, the distal portion of the wing orbracket can, alternatively or additionally, be angled inward or outwardto facilitate bone anchor placements having a medial trajectory (i.e.,towards the middle of a patient) or a lateral trajectory (i.e., towardsthe side of a patient). Such angulation can facilitate improvedengagement or purchase of the auxiliary anchor to bone and/or access bya driver instrument to the bone anchor opening of the wing.

FIGS. 5A through SI illustrate an exemplary embodiment of a bone anchorassembly 500 that includes a bracket or wing 530 having an angled distalportion 530 d. When viewed from the perspective of FIG. 5A, the distalportion 530 d is angled towards the right side of the wing 530. The boneanchor assembly 500 can include a bone anchor 502, a receiver member504, a closure mechanism 508, a bracket or wing 530, a nut 532 and anauxiliary bone anchor 534. The wing 530 can be secured to the receivermember 504, e.g., using the closure mechanism 508 and nut 532, therebyproviding the ability to augment fixation of the bone anchor 502 withthe auxiliary bone anchor 534 having an angular trajectory. The closuremechanism 508 can be secured to the receiver member 504 to capture aspinal fixation element, e.g., a spinal rod 506, within the receivermember. Tightening or locking the closure mechanism 508 can be effectiveto fix the spinal rod 506 relative to the receiver member 504, and tofix an angular position of the bone anchor 502 relative to the receivermember 504.

Except as described below or as will be readily appreciated by onehaving ordinary skill in the art, the bone anchor 502, the receivermember 504, the closure mechanism 508, the nut 532, and the auxiliarybone anchor 534 are substantially similar to the bone anchor 202, thereceiver member 204, the closure mechanism 208, the nut 232, and theauxiliary bone anchors 234 described above with respect to FIGS. 2A-2M.A detailed description of the structure and function thereof is thusomitted here for the sake of brevity. The bone anchor assembly 500 caninclude any one or more of the features of the bone anchor assembly 200and/or the bone anchor assembly 100 described above.

In the illustrated embodiment, the bracket or wing 530 can include aproximal portion 530 p, an angled distal portion 530 d, and a spanningportion 530 s that connects the proximal portion to the distal portionof the wing. The proximal portion 530 p of the wing 530 can extendhorizontally from a proximal end of the spanning portion 530 s of thewing 530. The proximal portion 530 p can include a proximal-facingsurface 540 and a distal-facing surface 542. The proximal-facing surface540 of the proximal portion 530 p of the wing 530 can be domed orrounded to provide an atraumatic surface and reduce the risk of tissueirritation post-implantation. The distal-facing surface 542 of theproximal portion 530 p of the wing 530 can be configured to bear againsta proximal terminal end or surface of the receiver member 504. Thedistal-facing surface 542 can form a negative or a substantial negativeof the proximal terminal end or surface of the receiver member 504. Forexample, the proximal-facing surfaces of the arms of the receiver member504 can be radially-convex, and the distal-facing surface 542 of thewing 530 can define a radially-concave channel (not shown) that receivesthe convex ends of the arms.

The proximal portion 530 p of the wing 530 can define a central opening536 that extends through the proximal-facing surface 540 and thedistal-facing surface 542. The central opening 536 can be oriented suchthat the central axis of the opening A3 is perpendicular orsubstantially perpendicular to the distal-facing surface 542 of theproximal portion 530 p of the wing 530. The central opening 536 can besized so that the closure mechanism 508 can be inserted through theopening and extend at least partially above the proximal-facing surface540 of the proximal portion 530 p of the wing 530. The central opening536 can include a smooth, non-threaded interior surface to allow thewing 530 and the closure mechanism 508 to be freely rotatable withrespect to one another. The central opening 536 or another feature ofthe wing 530 can be sized and configured to snap onto or capture aportion of the closure mechanism 508 or a proximal surface of thereceiver member 504. In the illustrated exemplary embodiment, acounter-bore 560 can be formed about the central opening 536 in thedistal-facing surface 542 of the proximal portion 530 p of the wing 530to accommodate a radially extending shoulder portion of the closuremechanism 508 that may extend above the proximal terminal end of thereceiver member 504. The structure and function of the counter-bore 560is discussed in more detail with respect to FIG. 6A-6C.

The spanning portion 530 s of the wing 530 can extend vertically in aproximal-distal direction to join the proximal portion 530 p of the wingto the distal portion 530 d of the wing. The spanning portion 530 s ofthe wing 530 can be an elongated arm that extends distally from a sidewall of the proximal portion 530 p of the wing in a vertical or asubstantially vertical plane. The spanning portion 530 s of the wing 530can have a lateral surface 550 that engages or faces a sidewall of thereceiver member 504. The lateral surface 550 can form a negative of thesidewall of the receiver member 504, such that the spanning portion 530s of the wing 530 can hug the receiver member with minimal or zero gapthere between. For example, the lateral surface 550 can be concave witha radius of curvature equal or substantially equal to a radius ofcurvature of the exterior sidewall of the receiver member 504. Theproximal portion 530 p, distal portion 530 d, and spanning portion 530 scan be formed integrally as a monolithic unit as shown, or one or moreof said components can be separate and selectively attachable to theothers. In some embodiments, a kit of modular components can be providedto allow selection of the components most appropriate for a given use.For example, a spanning portion 530 s of appropriate height can beselected based on the distance between the proximal end of the receivermember 504 and the bone surface in a given application.

In some embodiments, the wing 530 can include various features of aunilateral locking interface, including but not limited to one or moregrooves 570 a, 570 b, and surface projections 570 c. The unilaterallocking interface enables a surgical instrument that includes aunilateral locking mechanism (not shown) to rigidly hold onto one sideof the wing 530. Exemplary unilateral locking interfaces that can beincluded in the wing 530 are disclosed in U.S. patent application Ser.No. 15/843,618, filed on Dec. 15, 2017 and entitled “Unilateral ImplantHolders and Related Methods,” the entire contents of which are herebyincorporated by reference.

The angled distal portion 530 d of the wing 530 can extend outward fromthe distal end of the spanning portion 530 s away from the receivermember 504. The degree to which the wing 530 extends outward from thereceiver member 504 can vary among different embodiments. In theillustrated embodiment, the ratio of wing extension to rod diameter (orthe ratio of wing extension to the width of the rod-receiving recess inthe receiver member) is about 2:1. In some embodiments, this ratio canbe less than about 10:1, less than about 5:1, less than about 3:1, lessthan about 2:1, less than about 1:1, and/or less than about 0.5:1. Insome embodiments, the ratio can be about 10:1, about 5:1, about 3:1,about 2:1, about 1:1, or about 0.5:1.

When viewed from the perspective of FIG. 5E, the angled distal portion530 d is angled to the right of the vertically-disposed spanning portion530 s of the wing 530. As shown, the angled distal portion 530 dincludes a distal surface 546 and a proximal surface 548. The distalsurface 546 and the proximal surface 548 can be oriented in parallel orsubstantially in parallel. The distal-facing surface 546 can includeteeth, texturing, or other surface features to enhance grip with theadjacent bone. The distal portion 530 d of the wing 530 can have alateral surface 552 that abuts or faces a sidewall of the receivermember 504. The lateral surface 552 can form a negative of the sidewallof the receiver member 504, such that the distal-portion 530 d of thewing 530 can hug the receiver member with minimal or zero gap therebetween. For example, the lateral surface 552 can be concave with aradius of curvature equal or substantially equal to a radius ofcurvature of the exterior sidewall of the receiver member 504.

The distal portion 530 d of the wing 530 can define an opening 544 thatextends through the proximal surface 548 and the distal surface 546 toreceive an auxiliary bone anchor 534. The bone anchor opening 544 can besized to insert a distal shaft of the auxiliary bone anchor 534 throughthe opening and to abut the proximal head of the auxiliary bone anchorwhen disposed therein. As shown in the illustrated embodiment, the boneanchor opening 544 can be oriented perpendicular or substantiallyperpendicular to the distal surface 546 of the wing 530. In otherarrangements, the nominal or central axis of the bone anchor opening canbe obliquely angled relative to the distal surface 546 and/or theproximal surface 548. The distal surface 546 of the wing 530 and/or theproximal surface 548 of the wing can be obliquely angled relative to avertical or proximal-distal axis of the wing. For example, as shown, thedistal surface 546 is angled to face to the right of thevertically-disposed spanning portion 530 s. In such embodiments, thecentral axis A2 of the bone anchor opening 544 can extend at an obliqueangle, down and to the right, with respect to a proximal-distal axis A1of the spanning portion 530 s of the wing. This arrangement canfacilitate various bone anchor placements in which the distal end of theauxiliary bone anchor is to the right of the spanning portion 530 s ofthe wing when viewed from the perspective of FIG. 5A.

For example, as shown in FIG. 5A, such bone anchor placements caninclude ones in which the wing 530 is disposed laterally to a spinal rod506 and in which the auxiliary bone anchor 534 is driven through thebone anchor opening 544 with a cephalad trajectory (i.e., towards apatient's head). This orientation can allow the auxiliary bone anchor534 to remain wholly within the same vertebral level as the primary boneanchor 502, for example within a lateral mass of the vertebra. It willbe appreciated that the wing 530 can be flipped around to be positionedon the other side of the illustrated rod 506 (e.g., on a medial side ofthe rod), or to be positioned laterally to a contralateral spinal rod(not shown). In these cases, the positioning of the wing 530 canfacilitate bone anchor placements in which the auxiliary bone anchor 534can be driven through the bone anchor opening 544 with a caudaltrajectory (i.e., towards a patient's feet). In some embodiments, asdiscussed further below with respect to FIG. 7A, a caudal trajectory canallow for fixation of the auxiliary bone screw 534 into multiplecortical bone layers, e.g., at least two, at least three, or more. Theangled distal portion 530 d can allow for the above described boneanchor placements while maintaining the distal surface 546 of the wing530 in contact with or in close proximity to the bone surface (e.g.,within 0 to 3 mm).

In some embodiments, depending on the requirements of the particularapplication, the distal surface 546 of the wing 530 can be obliquelyangled to fix the central axis A2 of the bone anchor opening 544 at anyoblique angle to the right of the spanning portion 530 s of the wing530. For example, as shown in FIGS. 5E, the distal surface 546 of thedistal portion 530 d of the wing 530 can be obliquely angled, such thatthe central axis A2 of the bone anchor opening 544 extends at an angleof 35 degrees to the right of the proximal-distal axis A1 of thespanning portion 530 s of the wing 530. Thus, an auxiliary bone anchor534 can be readily disposed in the bone anchor opening 544 with thedistal shaft of the anchor having an angular trajectory coaxial with, orwithin a defined cone of angulation with respect to, the central axis A2of the bone anchor opening 544 to the right of the spanning portion 530s. In some embodiments, the distal surface 546 of the wing 530 can beobliquely angled, such that the central axis A2 of the bone anchoropening 544 can extend at an angle between 15 to 45 degrees inclusive tothe right of the proximal-distal axis A1 of the spanning portion 530 s.

In some embodiments, the distal surface 546 of the wing 530 can befurther angled to face inward or outward with respect to thevertically-disposed spanning portion 530 s of the wing 530. By anglingthe distal surface 546 inward or outward, the distal portion 530 d canfacilitate auxiliary bone anchor placements through the bone anchoropening 544 having a medial or lateral trajectory component in additionto or instead of a cephalad or caudal trajectory component. In someembodiments, angling the distal surface 546 inward or outward canfacilitate bone anchor placements in which the auxiliary bone anchor 534is secured within the lateral mass of a vertebra. In some embodiments,angling the distal surface 546 of the wing 530 inward or outward canprovide clearance for a driver instrument on the proximal surface 548side of the distal portion 530 d of the wing 530 to access the boneanchor opening 544. In some embodiments, based on the requirements ofthe particular application, the distal surface 546 of the wing 530 canbe obliquely angled inward or outward to fix the central axis A2 of thebone anchor opening 544 at any medial or lateral angle with respect to aproximal-distal axis A1 of the spanning portion 530 s of the wing 530.For example, as shown in FIG. 5F, the distal surface 546 of the distalportion 530 d of the wing 530 can be angled to face inward towards thespanning portion 530 s of the wing 530, such that the central axis A2 ofthe bone anchor opening 544 extends inward at a medial angle of 15degrees with respect to the proximal-distal axis A1 of the spanningportion 530 s. Thus, an auxiliary bone anchor 534 can be readilydisposed in the bone anchor opening 544 with the distal shaft of theanchor having a medial trajectory coaxial with, or within a defined coneof angulation with respect to, the central axis A2 of the bone anchoropening 544. In some embodiments, the distal surface 546 of the distalportion 530 d of the wing 530 can be obliquely angled, such that thecentral axis A2 of the bone anchor opening 544 can extend at a medialangle between 5 to 20 degrees inclusive.

Alternatively, as shown in FIG. 5G, the distal surface 546 of the distalportion 530 d of the wing 530 can be angled to face outward away fromthe spanning portion 530 s, such that the central axis A2 of the boneanchor opening 544 extends outward at a lateral angle of 15 degrees withrespect to the proximal-distal axis A1 of the spanning portion 530 s ofthe wing 530. Thus, an auxiliary bone anchor 534 can be readily disposedin the bone anchor opening 544 with the distal shaft of the anchorhaving a lateral trajectory coaxial with, or within a defined cone ofangulation with respect to, the central axis A2 of the bone anchoropening 544. In some embodiments, the distal surface 546 of the distalportion 530 d of the wing 530 can be obliquely angled, such that thecentral axis A2 of the bone anchor opening 544 can extend at a lateralangle between 5 to 20 degrees inclusive. Such embodiments can be usefulto accommodate the bony anatomy of the lumbar spine.

FIG. 5H is a top view of the wing 530 of the bone anchor assembly ofFIG. 5A with the angled distal portion 530 d facing in a caudaldirection. As shown in FIG. 5H, from a posterior viewpoint, the wing 530can be positioned with the angled distal portion 530 d extendinglaterally relative to the left of the spinal midline and thus facing ina caudal direction. In this exemplary caudal configuration, the angleddistal portion 530 d of the wing 530 has a superior end 580, an inferiorend 582, a free lateral end 584 extending between the superior andinferior ends, and a medial end 586 extending between the superior andinferior ends. With the angled distal portion 530 d facing caudally, thesuperior end 580 of the distal portion 530 d is more distal (or lower)than the inferior end 582, such that the distal surface 546 faces in thecaudal direction. In some embodiments, when the distal portion 530 d isalso angled medially (e.g., as discussed above in FIG. 5F), the superiorend 580 of the distal portion 530 d is more distal than the inferior end582 and the free lateral end 584 is more distal than the medial end,such that the distal surface 546 faces in both caudal and medialdirections. In some embodiments, when the distal portion 530 d is alsoangled laterally (e.g., as discussed above in FIG. 5G), the superior end580 of the distal portion 530 d is more distal than the inferior end 582and the medial end 586 is more distal than the free lateral end 584,such that the distal surface 546 faces in both caudal and lateraldirections.

FIG. 5I is a top view of the wing 530 of the bone anchor assembly ofFIG. 5A with the angled distal portion 530 d facing in a cephaladdirection. As shown in FIG. 5I, from a posterior viewpoint, the wing 530can be positioned with the distal portion 530 d extending laterallyrelative to the right of the spinal midline and thus facing in acephalad direction. In this exemplary cephalad configuration, the angleddistal portion 530 d of the wing 530 has a superior end 590, an inferiorend 592, a free lateral end 594 extending between the superior andinferior ends, and a medial end 596 extending between the superior andinferior ends. With the distal portion 530 d facing cephalically, theinferior end 592 of the distal portion 530 d is more distal (or lower)than the superior end 590, such that the distal surface 546 faces in acephalad direction. In some embodiments, when the distal portion 530 dis also angled medially (e.g., as discussed above in FIG. 5F), theinferior end 592 of the distal portion 530 d is more distal (or lower)than the superior end 590 and the free lateral end 594 is more distalthan the medial end 596, such that the distal surface 546 faces in bothcephalad and medial directions. In some embodiments, when the distalportion 530 d is also angled laterally (e.g., as discussed above in FIG.5G), the inferior end 592 of the distal portion 530 d is more distal (orlower) than the superior end 590 and the medial end 596 is more distalthan the free lateral end 594, such that the distal surface 546 faces inboth cephalad and lateral directions.

In some embodiments, the bone anchor opening 544 can include any of anumber of features for accepting bone anchors 534 at varying angles. Forexample, as discussed above with respect to FIG. 2A-2M, the bone anchoropening 544 can be at least partially threaded to receive avariable-angle locking screw having a threaded proximal head. As shown,the opening 544 can have a plurality of columns of threads spaced apartto define a plurality of non-threaded recesses. In the illustratedembodiment, the opening 544 has four columns of threads. The columns ofthreads can be arranged around the inner surface of the opening 544 forengaging threads on the head of a locking auxiliary bone anchor and/or avariable-angle locking auxiliary bone anchor. The auxiliary bone anchor534 can thus be locked with the wing 530 coaxially with the central axisA2 of the opening 544 or at a selected angle within a range ofselectable angles relative to the central axis A2 of the opening 544.The auxiliary bone anchor 534 can include features to facilitate thisvariable-angle locking, such as a proximal head that is at leastpartially spherical having a thread with a profile that follows thearc-shaped radius of curvature of the spherical portion of the head. Thevariable-angle capability of the screw/opening interface can allow theuser to place a locking auxiliary bone anchor into the bone at any anglewithin defined angulation limits. In some embodiments, the interiorsurface of the opening 544 can be smooth or spherical, without threadsor locking features.

In some embodiments, the proximal-most extent of each auxiliary boneanchor 534 can be distal to the spinal rod 506. In other embodiments,the proximal-most extent of each auxiliary bone anchor 534 can be distalto the distal-most extent of the receiver member 504. Theseconfigurations can advantageously reduce the overall profile of theassembly 500. The wing 500 can be Z-shaped or substantially Z-shaped.While one bone anchor opening 544 is shown in the illustratedembodiment, it will be appreciated that the wing 530 can include anynumber of bone anchor openings (e.g., one, two, three, four, five, andso on).

FIG. 6A-6C are cross-sectional views illustrating the wing or bracket530 secured to the bone anchor assembly 500 of FIG. 5A-5H. As discussedabove, the proximal portion 530 p of the wing can include adistal-facing surface 542 configured to bear against a proximal terminalend or surface of the receiver member 504 when the wing 530 is securedto the receiver member. For example, in some embodiments, the closuremechanism 508 can be in the form of a threaded post having anenlarged-diameter distal portion 508 d and a reduced-diameter proximalportion 508 p. The distal portion 508 d of the closure mechanism 508 canbe threaded into the receiver member 504 to engage a spinal rod 506disposed in the receiver member. The proximal portion 508 p of theclosure mechanism 508 can protrude above the receiver member 504, e.g.,above a proximal-facing terminal end or surface of the receiver member,and through the opening 536 formed in the wing.

However, there can be instances when the distal portion 508 d of theclosure mechanism 508 may not be fully threaded into the receiver member504, which can cause the radially-extending shoulder portion 508 s ofthe closure mechanism 508 to protrude above the proximal end of thereceiver member 504. In such instances, the shoulder portion 508 s ofthe closure mechanism 508 can abut the proximal portion 530 p of thewing 530 distal-facing surface 542 of the wing and thereby prevent theproximal portion 530 p from bearing against the receiver member 504.This can cause less reliable and/or inconsistent tightening of the wing530 to the bone anchor assembly 500.

As shown in the illustrated embodiment of FIGS. 6A and 6B, a counterbore 560 can be formed about the opening 536 in the distal-facingsurface 542 of the proximal portion 530 p to secure the wing 530 to thebone anchor assembly 500 more consistently. The counter bore 560 can bean annular ring or channel formed around the opening 536. The counterbore 560 can be sized to accommodate the width of the shoulder portion508 s. The depth or height of the counter bore 560 can be configured toat least partially receive the shoulder portion 508 s that protrudesabove the receiver member 504 in order to maintain contact between theproximal portion 530 p of the wing 530 and the proximal-facing surfaceof the receiver member 504. The depth or height of the counter bore 560can be configured not to exceed a threshold depth or height at which theclosure mechanism can become disengaged from the spinal rod and thuscompromise fixation of the rod 506 within the receiver member 504.Embodiments including a counterbore can provide more reliable and/orconsistent tightening by ensuring that the wing is always tightened tothe receiver member, regardless of the vertical position of the closuremechanism.

Alternatively or additionally, as shown in the illustrated embodiment ofFIG. 6C, the closure mechanism 508 can be sized such that theradially-extending shoulder portion 508 s is configured to always extendabove the receiver member 504. In such embodiments, the distal-facingsurface 542 of the proximal portion 530 d of the wing 530 bears againstthe radially-extending shoulder portion 508 s of the closure mechanism508 instead of the receiver member 504. For example, as shown in FIG.6C, the enlarged-diameter distal portion 508 d of the closure mechanism508 can be configured with an extended height H that allows the shoulderportion 508 s of the closure mechanism 508 to protrude above thereceiver member 504 when in contact with the spinal rod 506. Suchembodiments can provide a more reliable and/or consistent tightening ofthe wing 530 by ensuring that the wing is always tightened to theclosure mechanism, regardless of the vertical position of the closuremechanism.

As discussed above, some embodiments of the bone anchor assembly caninclude a wing having a distal portion angled to the left of thevertically-disposed wing. In such embodiments, an auxiliary bone anchorcan be disposed through an opening in the distal portion with caudal orcephalad trajectories similar to those facilitated by the wing 530 ofthe bone anchor assembly 500 when implanted on the opposite side of thepatient's spine (i.e., the left hand side of the patient).

FIGS. 7A through 7F illustrate an exemplary embodiment of a bone anchorassembly 700 that includes a bracket or wing 730 having an angled distalportion 730 d. As shown, the bone anchor assembly 700 includes a boneanchor 502, a receiver member 504, a closure mechanism 508, a bracket orwing 730, a nut 532 and an auxiliary bone anchor 534. Except asdescribed below or as will be readily appreciated by one having ordinaryskill in the art, the bone anchor 502, the receiver member 504, theclosure mechanism 508, the nut 532, and the auxiliary bone anchor 534are substantially similar to the bone anchor 202, the receiver member204, the closure mechanism 208, the nut 232, and the auxiliary boneanchors 234 described above with respect to FIGS. 2A-2M. A detaileddescription of the structure and function thereof is thus omitted herefor the sake of brevity. The bone anchor assembly 500 can include anyone or more of the features of the bone anchor assembly 200 and/or thebone anchor assembly 100 described above.

As shown in FIGS. 7A through 7F, the bracket or wing 730 can include aproximal portion 730 p, an angled distal portion 730 d, and a spanningportion 730 s that connects the proximal portion to the distal portionof the wing. Except as described below or as will be readily appreciatedby one having ordinary skill in the art, the proximal portion 730 p andthe spanning portion 730 s of the wing 730 are substantially similar tothe proximal portion 530 p and the spanning portion 530 s of the wing530 described above with respect to FIGS. 5A-5I and FIGS. 6A-6C. Adetailed description of the structure and function thereof is thusomitted here for the sake of brevity. The wing 730 can include any oneor more of the features of the wing 500 described above.

In the illustrated embodiment, the distal portion 730 d of the wing 730is substantially similar to the distal portion 530 d of the wing 500,except that the distal portion 730 d is angled to the left of thevertically-disposed spanning portion 730 s (when viewed from theperspective of FIG. 7D). As shown, the angled distal portion 730 d caninclude a distal surface 746 and a proximal surface 748 that can beoriented in parallel or substantially in parallel. The distal portion730 d of the wing 730 can define an opening 744 that extends through theproximal surface 748 and the distal surface 746 to receive an auxiliarybone anchor 534. As shown in the illustrated embodiment, the bone anchoropening 744 can be oriented perpendicular or substantially perpendicularto the distal surface 746 of the wing 730. In other arrangements, thenominal or central axis of the bone anchor opening can be obliquelyangled relative to the distal surface 746 and/or the proximal surface748. The distal surface 746 of the wing 730 and/or the proximal surface748 of the wing can be obliquely angled relative to a vertical orproximal-distal axis of the wing. For example, as shown, the distalsurface 546 is angled to face to the left of the vertically-disposedspanning portion 730 s. In such embodiments, the central axis A2 of thebone anchor opening 744 can extend at an oblique angle, down and to theleft, with respect to the proximal-distal axis A1 of the spanningportion 730 s of the wing. This arrangement can facilitate various boneanchor placements in which the distal end of the auxiliary bone anchoris to the left of the spanning portion 530 s of the wing when viewedfrom the perspective of FIG. 7A.

For example, as shown in FIG. 7A, such bone anchor placements caninclude ones in which the wing 730 is disposed laterally to a spinal rod506 and in which the auxiliary bone anchor 534 is driven through thebone anchor opening 744 with a caudal trajectory (i.e., towards apatient's feet). This orientation can allow the auxiliary bone anchor534 to extend into one or more adjacent vertebral levels, e.g., across afacet joint. A caudal trajectory can allow for fixation of the auxiliarybone screw 534 into multiple cortical bone layers, e.g., at least two,at least three, or more. For example, as shown in FIG. 7A, with theprimary bone anchor 502 positioned in a superior vertebral level, thebone anchor assembly 700 can effect tri-cortical fixation with theauxiliary bone anchor 534 crossing a facet joint between the superiorvertebral level and an adjacent inferior vertebral level. It will beappreciated that the wing 730 can be flipped around to be positioned onthe other side of the illustrated rod 506 (e.g., on a medial side of therod), or to be positioned laterally to a contralateral spinal rod (notshown). In these cases, the positioning of the wing 530 can facilitatebone anchor placements in which the auxiliary bone anchor 534 can bedriven through the bone anchor opening 744 with a cephalad trajectory(i.e., towards a patient's head). As discussed above with respect toFIG. 5A, a cephalad trajectory can allow the auxiliary bone anchor 534to remain wholly within the same vertebral level as the primary boneanchor 502, for example within a lateral mass of the vertebra. Theangled distal portion 730 d can allow for the above-described boneanchor placements while maintaining the distal surface 746 of the wing730 in contact with or in close proximity to the bone surface (e.g.,within 0 to 3 mm).

In some embodiments, depending on the requirements of the particularapplication, the distal surface 746 of the wing 730 can be obliquelyangled to fix the central axis A2 of the bone anchor opening 744 at anyoblique angle to the left of the spanning portion 730 s of the wing 730.For example, as shown in FIG. 7D, the distal surface 746 of the distalportion 730 d of the wing 730 can be obliquely angled, such that thecentral axis A2 of the bone anchor opening 744 extends at an angle of 35degrees to the left of the proximal-distal axis A1 of the spanningportion 730 s of the wing 730. Thus, an auxiliary bone anchor 534 can bereadily disposed in the bone anchor opening 744 with the distal shaft ofthe anchor having an angular trajectory coaxial with, or within adefined cone of angulation with respect to, the central axis A2 of thebone anchor opening 744 to the left of the spanning portion 730 s. Insome embodiments, the distal surface 746 of the wing 730 can beobliquely angled, such that the central axis A2 of the bone anchoropening 744 can extend at an angle between 15 to 45 degrees inclusive tothe left of the proximal-distal axis A1 of the spanning portion 730 s.

As discussed above with respect to FIGS. 5F and 5G, in some embodiments,the distal surface 746 of the wing 730 can be further angled to faceinward or outward with respect to the vertically-disposed spanningportion 730 s of the wing 730. In some embodiments, based on therequirements of the particular application, the distal surface 746 ofthe wing 730 can be obliquely angled inward or outward to fix thecentral axis A2 of the bone anchor opening 744 at any medial or lateralangle between 5 and 20 degrees inclusive with respect to aproximal-distal axis A1 of the spanning portion 730 s of the wing 730.Thus, by angling the distal surface 746 inward or outward, the distalportion 730 d can facilitate placement of the auxiliary bone anchor 534having a medial or lateral trajectory component in addition to orinstead of a cephalad or caudal trajectory component through the boneanchor opening 744. In some embodiments, angling the distal surface 746inward or outward can facilitate bone anchor placements in which theauxiliary bone anchor 534 is secured within the lateral mass of avertebra. In some embodiments, angling the distal surface 746 of thewing 730 inward or outward can provide clearance for a driver instrumenton the proximal surface 748 side of the distal portion 730 d of the wing730 to access the bone anchor opening 744.

FIG. 7E is a top view of the wing 730 of the bone anchor assembly ofFIG. 7A with the angled distal portion 730 d facing in a cephaladdirection. As shown in FIG. 7E, from a posterior viewpoint, the wing 730can be positioned with the distal portion 730 d extending laterallyrelative to the left of the spinal midline and thus facing in a cephaladdirection. In this exemplary cephalad configuration, the angled distalportion 730 d of the wing 730 has a superior end 780, an inferior end782, a free lateral end 784 extending between the superior and inferiorends, and a medial end 786 extending between the superior and inferiorends. With the distal portion 730 d facing cephalically, the inferiorend 782 of the distal portion 730 d is more distal (or lower) than thesuperior end 780, such that the distal surface 746 faces in a cephaladdirection. In some embodiments, when the distal portion 730 d is alsoangled medially (e.g., as discussed above in FIG. 5G), the inferior end782 of the distal portion 730 d is more distal (or lower) than thesuperior end 780 and the free lateral end 784 is more distal than themedial end 786, such that the distal surface 746 faces in both cephaladand medial directions. In some embodiments, when the distal portion 730d is also angled laterally (e.g., as discussed above in FIG. 5H), theinferior end 782 of the distal portion 730 d is more distal (or lower)than the superior end 780 and the medial end 786 is more distal than thefree lateral end 784, such that the distal surface 746 faces in bothcephalad and lateral directions.

FIG. 7F is a top view of the wing 730 of the bone anchor assembly ofFIG. 7A with the angled distal portion 730 d facing in a caudaldirection. As shown in FIG. 7F, from a posterior viewpoint, the wing 730can be positioned with the angled distal portion 730 d extendinglaterally relative to the right of the spinal midline and thus facing ina caudal direction. In this exemplary caudal configuration, the angleddistal portion 730 d of the wing 730 has a superior end 790, an inferiorend 792, a free lateral end 794 extending between the superior andinferior ends, and a medial end 796 extending between the superior andinferior ends. With the angled distal portion 730 d facing caudally, thesuperior end 790 of the distal portion 730 d is more distal (or lower)than the inferior end 792, such that the distal surface 746 faces in thecaudal direction. In some embodiments, when the distal portion 730 d isalso angled medially (e.g., as discussed above in FIG. 5G), the superiorend 790 of the distal portion 730 d is more distal than the inferior end792 and the free lateral end 794 is more distal than the medial end 796,such that the distal surface 746 faces in both caudal and medialdirections. In some embodiments, when the distal portion 730 d is alsoangled laterally (e.g., as discussed above in FIG. 5H), the superior end790 of the distal portion 730 d is more distal than the inferior end 792and the medial end 796 is more distal than the free lateral end 794,such that the distal surface 746 faces in both caudal and lateraldirections.

As discussed above, some embodiments of the bone anchor assembly caninclude a wing having a distal portion angled inward or outward withrespect to the vertically-disposed spanning portion without any right orleft angulation. In such embodiments, an auxiliary bone anchor can bereadily disposed through a bone anchor opening in the distal portionwith a medial trajectory or a lateral trajectory.

FIGS. 8A through 8E illustrate an exemplary embodiment of a bracket orwing 830 of a bone anchor assembly having an angled distal portion 830d. As shown, the bracket or wing 830 can include a proximal portion 830p, an angled distal portion 830 d, and a spanning portion 830 s thatconnects the proximal portion to the distal portion. The angled distalportion 830 d has a free lateral end 850 and a medial end 852. Except asdescribed below or as will be readily appreciated by one having ordinaryskill in the art, the proximal portion 830 p and the spanning portion830 s of the wing 830 are substantially similar to the proximal andspanning portions of the wing 200, 500, and/or 700 described above withrespect to FIGS. 2A-2M, 5A-5I, and 7A-7F. A detailed description of thestructure and function thereof is thus omitted here for the sake ofbrevity. The wing 830 include any one or more of the features of thewings 200, 500 and/or 700 described above.

In the illustrated embodiment, the distal portion 830 d of the wing 830is substantially similar to the angled distal portions 530 d, 730 ddisclosed above with respect to FIGS. 5A-5I and 7A-7F, except that thedistal portion 830 d is angled inward towards the vertically-disposedspanning portion 830 s without angulation to the right or left of thewing 830 s. The angled distal portion 830 d of the wing 830 includes adistal surface 846 and a proximal surface 848. The distal surface 846and the proximal surface 848 can be tilted down in parallel orsubstantially in parallel. When the distal portion 830 d is angledinward (or medially when viewed from the perspective of FIG. 8B), thefree lateral end 850 is more distal than the medial end 852, such thatthe distal surface 846 faces in a medial direction.

The distal portion 830 d of the wing 830 can define one or more openings844 that extend through the proximal surface 848 and the distal surface846 to receive an auxiliary bone anchor 534. As shown in the illustratedembodiment, the bone anchor openings 844 can be oriented perpendicularor substantially perpendicular to the distal surface 846 of the wing830. The distal surface 846 of the wing 830 can be obliquely angled toface inward towards the vertically-disposed spanning portion 830 s ofthe wing 830 to fix the central axis A2 of the bone anchor opening 844at a medial angle with respect to the proximal-distal axis A1 of thespanning portion 830 s. Thus, an auxiliary bone anchor 534 can bereadily disposed in the bone anchor opening 844 with the distal shaft ofthe auxiliary bone anchor 534 having a medial trajectory coaxial with,or within a defined cone of angulation with respect to, central axis A2of the bone anchor opening.

For example, in the illustrated embodiment of FIG. 8D, the distalsurface 846 of the distal portion 830 d of the wing 830 can be angled toface inward towards the spanning portion 830 s, such that the centralaxis A2 of the bone anchor opening 844 extends inward at an angle of 15degrees with respect to the proximal-distal axis A1. Thus, the auxiliarybone anchor 534 can be readily disposed in the bone anchor opening 844with the distal shaft of the anchor having an medial trajectory of 15degrees with respect to the proximal-distal axis A1. In someembodiments, the distal surface 846 of the distal portion 830 d of thewing 830 can be obliquely angled to fix the central axis A2 of the boneanchor opening 844 at a medial angle between 5 to 20 degrees inclusivewith respect to the proximal-distal axis A1 of the spanning portion 830s of the wing 830. In such embodiments, angling the distal surface 846inward can facilitate bone anchor placements in which the auxiliary boneanchor 534 is secured within the lateral mass of a vertebra. In someembodiments, angling the distal surface 846 of the wing 830 inward canprovide clearance for a driver instrument on the proximal surface 848side of the distal portion 830 d of the wing 830 to access the boneanchor opening 544.

In an alternative embodiment shown in FIG. 8E, the distal portion 830 dcan be angled outward (or laterally, when viewed from the perspective ofFIG. 8E), such that the medial end 852 of the distal portion is moredistal than the free lateral end 850. In this lateral configuration, thedistal surface 846 faces outward away from the spanning portion 830 s ina lateral direction and the central axis A2 of the bone anchor opening844 extends outward at a lateral angle with respect to theproximal-distal axis A1 of the spanning portion 830 s of the wing 830.Thus, an auxiliary bone anchor 534 can be readily disposed in the boneanchor opening 844 with the distal shaft of the anchor having a lateraltrajectory coaxial with, or within a defined cone of angulation withrespect to, the central axis A2 of the bone anchor opening 844. In someembodiments, the distal surface 846 of the distal portion 830 d of thewing 830 can be obliquely angled, such that the central axis A2 of thebone anchor opening 844 can extend at a lateral angle between 5 to 20degrees inclusive (e.g., 15 degrees). In such embodiments, angling thedistal surface 846 outward can facilitate bone anchor placements inwhich the auxiliary bone anchor 534 is secured in a lateral location.Such embodiments can be useful to accommodate the bony anatomy of thelumbar spine.

An exemplary method of using the bone anchor assemblies disclosed hereinis described below.

The procedure can begin by forming an open or percutaneous incision inthe patient to access a bone in which a bone anchor assembly is to beimplanted. The bone can be prepared to receive the bone anchor assemblyas known in the art. For example, a pedicle of a vertebra can beprepared using standard awl, probe, and tap steps.

The bone anchor can then be advanced into the bone. If the user feelsthat the purchase of the bone anchor is inadequate, or that auxiliaryfixation would otherwise be desirable, an auxiliary fixation member canbe added to the bone anchor assembly.

For example, referring to the embodiment of FIGS. 2A-2M, a spinal rod206 can be seated in the receiver member 204 and a closure mechanism 208can be threaded down onto the rod. A wing 230 can then be positionedover the closure mechanism 208 and secured in place with the nut 232.One or more auxiliary bone anchors 234 can be inserted through the wing230 to attach the construct to the bone at a second location (or at morethan two locations). The method can include bending or flexing the wing230 to better fit the receiver member 204 or bone surface, for exampleby squeezing legs 258 of the wing together to increase a height of thewing.

As another example, referring to the embodiment of FIGS. 3A-3I, a plate360 can be seated in the receiver member 304 and a rod 306 can bepositioned over the plate and secured to the receiver member using aclosure mechanism 308. A cap 372 can be used if the height of the rod306 and plate 360 exceeds the design height of the receiver member 304.One or more auxiliary bone anchors 334 can be inserted through the plate360 to attach the construct to the bone at a second location (or at morethan two locations). The method can include bending or flexing the plate360 to better fit the receiver member 304 or bone surface.

As another example, referring to the embodiment of FIGS. 4A-4E, a spinalrod 406 can be seated in the receiver member 404 and a closure mechanism408 can be threaded down onto the rod. A collar 476 can then bepositioned over the receiver member 404 and secured to a hook 474 usinga locking screw 478. The hook 474 can be hooked onto a portion of thepatient's anatomy or a nearby implant to augment the fixation of thebone anchor assembly 400. The method can include bending or flexing thehook 474 to better fit the receiver member 404 or the anatomy orimplant.

As another example, referring to the embodiment of FIGS. 5A-5H, a spinalrod 506 can be seated in the receiver member 504 and a closure mechanism508 can be threaded down onto the rod. A wing 530 can be positioned overthe closure mechanism 508 and secured in place with the nut 532. Asdiscussed above, the wing 530 can include a distal portion 530 d that isangled to the right side of the wing 530. Thus, when the wing ispositioned lateral to a bone anchor disposed to the left of the spinalmidline when viewed from a posterior vantage point, an auxiliary boneanchor 534 can be inserted through the bone anchor opening 544 anddriven into bone with a caudal trajectory. When the wing is positionedlateral to a bone anchor disposed to the right of the spinal midlinewhen viewed from a posterior vantage point, an auxiliary bone anchor 534can be inserted through the bone anchor opening 544 and driven into bonewith a cephalad trajectory.

As another example, referring to the embodiment of FIGS. 7A-7F, a spinalrod 506 can be seated in the receiver member 504 and a closure mechanism508 can be threaded down onto the rod. A wing 730 can be positioned overthe closure mechanism 508 and secured in place with the nut 532. Asdiscussed above, the wing 730 can include a distal portion 730 d that isangled to the left side of the wing 730. Thus, when the wing ispositioned lateral to a bone anchor disposed to the left of the spinalmidline when viewed from a posterior vantage point, an auxiliary boneanchor 534 can be inserted through the bone anchor opening 744 anddriven into bone with a cephalad trajectory. When the wing is positionedlateral to a bone anchor disposed to the right of the spinal midlinewhen viewed from a posterior vantage point, an auxiliary bone anchor 534can be inserted through the bone anchor opening 744 and driven into bonewith a caudal trajectory.

As another example, referring to the embodiment of FIGS. 8A-8D, a spinalrod 506 can be seated in the receiver member 504 and a closure mechanism508 can be threaded down onto the rod. A wing 830 can be positioned overthe closure mechanism 508 and secured in place with the nut 532. Asdiscussed above in some embodiments, the wing 830 can include a distalportion 830 d that is angled to inward towards the spanning portion 830s of the wing 830. Thus, when the wing is positioned lateral to a boneanchor disposed to the left or right of the spinal midline when viewedfrom a posterior vantage point, an auxiliary bone anchor 534 can beinserted through the bone anchor opening 844 and driven into bone with amedial trajectory. In some embodiments, the wing 830 can include adistal portion 830 d that is angled to outward away from the spanningportion 830 s of the wing 830. Thus, when the wing is positioned lateralto a bone anchor disposed to the left or right of the spinal midlinewhen viewed from a posterior vantage point, an auxiliary bone anchor 534can be inserted through the bone anchor opening 844 and driven into bonewith a lateral trajectory.

The above steps can be repeated to install additional bone anchorassemblies at the same or at different vertebral levels, with or withoutauxiliary fixation members. Final tightening or other adjustment of theconstruct can be performed and the procedure can be completed usingknown techniques and the incision closed.

In any of the above embodiments or methods, the primary bone anchor canbe omitted and the user can rely solely on the one or more auxiliaryfixation features to secure the bone anchor assembly. This canadvantageously allow the position of the fixation to be completelyoffset from the receiver member, for example if an initially placed boneanchor needs to be removed due to improper positioning or inadequatepurchase, or when the receiver member needs to be positioned over alocation where a bone anchor cannot be inserted.

While the methods illustrated and described herein involve a bone anchorassembly placed in the pedicle or lateral mass of vertebral bone, itwill be appreciated that the systems and methods herein can be used inany bone, in non-bone tissue, or in non-living or non-tissue objects.

The auxiliary fixation members disclosed herein can be implanted in thesame surgical procedure as the bone anchor, receiver member, and spinalrod, or, in the case of revision surgery, during a subsequent surgicalprocedure.

It should be noted that any ordering of method steps expressed orimplied in the description above or in the accompanying drawings is notto be construed as limiting the disclosed methods to performing thesteps in that order. Rather, the various steps of each of the methodsdisclosed herein can be performed in any of a variety of sequences. Inaddition, as the described methods are merely exemplary embodiments,various other methods that include additional steps or include fewersteps are also within the scope of the present invention.

As evident from the foregoing, in at least some embodiments, the systemsand methods disclosed herein can provide enhanced fixation for a givensurgical site, providing greater bone fixation strength at a givenlocation without necessarily requiring moving the fixation to anadditional vertebra or skipping/increasing the involved vertebrallevels.

The bone anchor assemblies disclosed herein and the various componentparts thereof can be constructed from any of a variety of knownmaterials. Exemplary materials include those which are suitable for usein surgical applications, including metals such as stainless steel,titanium, or alloys thereof, polymers such as PEEK, ceramics, carbonfiber, and so forth. The various components of the devices disclosedherein can be rigid or flexible. One or more components or portions ofthe device can be formed from a radiopaque material to facilitatevisualization under fluoroscopy and other imaging techniques, or from aradiolucent material so as not to interfere with visualization of otherstructures. Exemplary radiolucent materials include carbon fiber andhigh-strength polymers.

The systems and methods disclosed herein can be used inminimally-invasive surgery and/or open surgery. While the systems andmethods disclosed herein are generally described in the context spinalsurgery, it will be appreciated that the systems and methods disclosedherein can be used with any human or animal implant, in any of a varietyof surgeries performed on humans or animals, and/or in fields unrelatedto implants or surgery.

Although specific embodiments are described above, it should beunderstood that numerous changes may be made within the spirit and scopeof the concepts described. Accordingly, it is intended that thisdisclosure not be limited to the described embodiments, but that it havethe full scope defined by the language of the following claims.

1. A bone anchor assembly, comprising: a bone anchor; an auxiliary boneanchor; a receiver member coupled to a proximal end of the bone anchorand defining a rod seat configured to receive a rod; a closure mechanismthreadably mated to the receiver member; a wing that includes a proximalportion, a distal portion, and a spanning portion that connects theproximal and distal portions, the proximal portion having adistal-facing surface that opposes a proximal terminal end of thereceiver member and defines an opening through which at least a portionof the closure mechanism is disposed, the spanning portion extendingvertically along a side wall of the receiver member between the proximalportion and the distal portion, the distal portion extending outwardfrom a distal end of the spanning portion; and a nut configured tothreadably engage the closure mechanism to secure the proximal portionof the wing to the receiver member, wherein the distal portion of thewing defines a bone anchor opening through which the auxiliary boneanchor is disposed and wherein a distal surface of the distal portion ofthe wing is obliquely angled relative to a proximal-distal axis of thespanning portion to face one of a caudal direction or a cephaladdirection.
 2. The bone anchor assembly of claim 1, wherein the distalsurface of the distal portion of the wing is obliquely angled to theright of the proximal-distal axis of the spanning portion.
 3. The boneanchor assembly of claim 1, wherein the distal surface of the distalportion of the wing is obliquely angled to the left of theproximal-distal axis of the spanning portion.
 4. The bone anchorassembly of claim 1, wherein the distal surface of the distal portion ofthe wing is obliquely angled relative to a proximal-distal axis of thespanning portion such that a central axis of the bone anchor openingextends in one of a caudal direction or a cephalad direction and in oneof a medial direction or a lateral direction when the wing is secured tothe receiver member.
 5. The bone anchor assembly of claim 4, wherein thedistal surface of the distal portion of the wing is obliquely angledinward and to the right of the proximal-distal axis of the spanningportion.
 6. The bone anchor assembly of claim 4, wherein the distalsurface of the distal portion of the wing is obliquely angled outwardand to the right of the proximal-distal axis of the spanning portion. 7.The bone anchor assembly of claim 4, wherein the distal surface of thedistal portion of the wing is obliquely angled inward and to the left ofthe proximal-distal axis of the spanning portion.
 8. The bone anchorassembly of claim 4, wherein the distal surface of the distal portion ofthe wing is obliquely angled outward and to the left of theproximal-distal axis of the spanning portion.
 9. The bone anchorassembly of claim 1, wherein a proximal surface of the distal portion ofthe wing is substantially parallel to the distal surface of the distalportion.
 10. The bone anchor assembly of claim 1, wherein the auxiliarybone anchor has a threaded proximal head and the bone anchor opening hasa partially threaded interior surface configured to engage the threadedproximal head of the auxiliary bone anchor such that the auxiliary boneanchor is capable of being locked at any angle amongst a plurality ofselectable angles relative to the central axis of the bone anchoropening.
 11. The bone anchor assembly of claim 1, wherein the closuremechanism comprises a threaded post having a radially extending shoulderportion and wherein a counter bore is formed about the opening in thedistal-facing surface of the proximal portion of the wing to accommodatethe radially extending shoulder portion extending at least partiallyabove the proximal terminal end of the receiver member.
 12. The boneanchor assembly of claim 1, wherein the bone anchor opening defined inthe distal portion of the wing comprises a plurality of bone anchoropenings. 13-21. (canceled)
 22. A method of securing a bone anchorassembly to bone, comprising: driving a bone anchor into bone, the boneanchor having a receiver member coupled to a proximal end thereof;positioning a rod in a rod seat defined in the receiver member;attaching a closure mechanism to the receiver member to retain the rodin the receiver member; coupling a proximal portion of a wing to atleast one of the closure mechanism and a proximal terminal end of thereceiver member, such that a spanning portion of the wing extendsvertically along a side wall of the receiver member between the proximalportion and a distal portion of the wing that extends outward from adistal end of the spanning portion; and driving the auxiliary boneanchor through a bone anchor opening formed in the distal portion of thewing into bone at an oblique angle in one of a caudal direction or acephalad direction, wherein a distal surface of the distal portion ofthe wing is obliquely angled relative to a proximal-distal axis of thespanning portion to face the caudal direction or the cephalad direction.23. The method of claim 22 wherein driving the auxiliary bone anchorthrough the bone anchor opening into bone comprises driving theauxiliary bone anchor through the bone anchor opening at an obliqueangle in a cephalad direction such that the bone anchor and theauxiliary bone anchor are respectively driven into a same vertebrallevel.
 24. The method of claim 22 wherein driving the auxiliary boneanchor through the bone anchor opening into bone comprises driving theauxiliary bone anchor through the bone anchor opening at an obliqueangle in a caudal direction such that the bone anchor and the auxiliarybone anchor are respectively driven into adjacent vertebral levels. 25.The method of claim 22, wherein the closure mechanism comprises athreaded post having a radially extending shoulder portion and whereincoupling the proximal portion of the wing to at least one of the closuremechanism and the proximal terminal end of the receiver membercomprises: disposing at least a portion of the threaded post through theopening formed in the proximal portion of the wing; and receiving theradially extending shoulder portion that extends at least partiallyabove the proximal terminal end of the receiver member in a counter boreformed about the opening in the distal-facing surface of the proximalportion of the wing.
 26. A method of securing a bone anchor assembly tobone, comprising: driving a bone anchor into bone, the bone anchorhaving a receiver member coupled to a proximal end thereof; positioninga rod in a rod seat defined in the receiver member; attaching a closuremechanism to the receiver member to retain the rod in the receivermember; coupling a proximal portion of a wing to at least one of theclosure mechanism and a proximal terminal end of the receiver member,such that a spanning portion of the wing extends vertically along a sidewall of the receiver member between the proximal portion and a distalportion of the wing that extends outward from a distal end of thespanning portion; and driving the auxiliary bone anchor through a boneanchor opening formed in the distal portion of the wing into bone at anoblique angle in one of a medial direction or a lateral direction,wherein a distal surface of the distal portion of the wing is obliquelyangled relative to a proximal-distal axis of the spanning portion toface the medial direction or the lateral direction.
 27. The method ofclaim 26 wherein driving the auxiliary bone anchor through the boneanchor opening into bone comprises driving the auxiliary bone anchorthrough the bone anchor opening at an oblique angle in the medialdirection such that the bone anchor and the auxiliary bone anchor arerespectively driven into a same vertebral level.
 28. The method of claim26 wherein driving the auxiliary bone anchor through the bone anchoropening into bone comprises driving the auxiliary bone anchor throughthe bone anchor opening at an oblique angle in the lateral directionsuch that the bone anchor and the auxiliary bone anchor are respectivelydriven into a same vertebral level.
 29. The method of claim 26, whereinthe closure mechanism comprises a threaded post having a radiallyextending shoulder portion and wherein coupling the proximal portion ofthe wing to at least one of the closure mechanism and the proximalterminal end of the receiver member comprises: disposing at least aportion of the threaded post through the opening formed in the proximalportion of the wing; and receiving the radially extending shoulderportion that extends at least partially above the proximal terminal endof the receiver member in a counter bore formed about the opening in thedistal-facing surface of the proximal portion of the wing. 30.(canceled)
 31. (canceled)